So BoLS did a couple articles on foot lists- or perhaps I should say that Goatboy did them (here and here, respectively.) He has the core of a point- in a mech-heavy environment, a foot army can have advantages by virtue of opponents being unprepared to face it properly. The problem, however, is that he makes the mistake of not going for foot lists that have all the critical advantages while avoiding disadvantages. There is a reason mech is king: it provides these advantages relatively easily. In order for foot to do well, it needs to likewise use them. This also has to do with BoLS' understanding of the game and believing in a metagame. Pure mech and foot lists have an advantage over other lists (particularly foot lists) as some of their weapons are essentially useless. Mech has this to a less extent than foot as there are always some foot elements to a mech army, you just have to get them out of their transports. Anyway, a lot of readers there seem to believe that taking non-mech is going against the 'meta' and gives them an advantage. Against lists 'metagaming' (i.e. tailoring) against mech lists, yes this gives them an advantage but against balanced lists? Not so.
Number one is mobility- missions in 5E want you to move about to take (and contest) points; getting into better positions to dictate charges, take side shots, bypass cover, etc, are all important factors. If a list doesn't have mobility, it is doomed. Mobility can be more than just moving over 6" per turn- it includes the list's overall ability to take points and get to the enemy as well as its reach/threat and deployment options.
Number two (WHO DOES NUMBER TWO WORK FOR??) is protection. When you're inside a metal box, you can't be hurt. Period. Obviously foot lists can't duplicate this, but they need a way to increase resilience above just "3+ armor/4+ cover". There are lots of ways to work this, including MSU options, resilience through numbers, etc, but you can't just be a bunch of bodies on the ground.
Number three is control; a mechanized list lets you affect your opponent's movement relative to you via blocking with tanks, choosing when to disembark, etc. A foot list needs to find way to take similar control of the battlefield; since tank shocking obviously isn't an option for them, the necessity to use bubblewrap and screening techniques becomes vital.
So let's look at some "good" foot lists and see how they use these techniques first, then we'll move onto some "bad" lists and see how they fail the criteria we've laid out.
Tyranids
The "Nidzilla" list (Tervigons, Tyrant, Hive Guard, Tyrannofexes) is an excellent example of how foot can work. At first glance it's rather poor- it can't move quickly, it can't really do anything, it just hopes to de-mech the enemy and nom them. It's actually deeper than that, however- like with a mech list, the mass of T6 wounds seeks to overwhelm the enemy's high-end firepower by taking advantage of target saturation. (That's Protection.) Moreover, it utilizes layered cover (Termagants protect Guard, Guard protect TFexes, TFexes protect Tervigons) to keep a constant 4++ against most everything, which helps mitigate the fact that there is no Damage Table to roll on. With all the guns being Assault and the list as a whole interested in moving closer to the enemy, Nidzilla is entirely capable of simply walking its way right into the other deployment zone- since it has good firepower even at mid-ranges, it can engage the enemy without having to be right next to them. It also has a strong theme of anti-tank, which it uses to break the back of the enemy's mobility and achieve superiority. Lastly, it makes extensive use of screening units- mainly Termagants- to insure that the enemy can't freely make disadvantageous assaults; acting, as it does, as a single entity, anything that comes close to part of it will quickly feel the wrath of the rest of the army.
Blood Angels
Unlike Tyranids BA has the option of playing mechanized, but foot lists are actually more of the default with the army when people think about them. Obviously they have Mobility- moving 12" per turn with the possibility of running makes them extremely fast, and they can also make varied deployments as needed. Protection comes from abundant bubbles of FNP- combined with cover, it basically makes their whole army into pseudo-Terminators, and killing off that many guys who are that tough is actually a very unpleasant proposition for most people, doubly so when placed on a short clock by their mobility. The army actually lacks in any good way to Control enemy movement, but its ability to bypass such tactics of the enemy (by virtue of jump infantry) makes it work reasonably well.
Space Wolves
Not the trashy list that Goatboy posted, the good version. Loganwing armies are perfectly capable of moving on foot and using the same strategy as Tyranids (i.e. "We move 6" every turn and can shoot, and good luck assaulting us") with more long-range fire support from Long Fangs but less scoring potential and resilience. Its Protection is the weak point- you're paying 18pts/body minimum and you're no tougher than any other Marine; on the other hand, most of your heavy weapons and special CCWs are protected by three or four ablative bodies. Control is another potential weak point- lacking screening units or the ability to hop the enemy, it is likely they will be faced with unfavorable charges much of the time. However, as with Tyranids, the intent is to deny the enemy all of their mobility and dare him to come to you. Having the Long Fangs for support is critical, as otherwise you just have those 10-12 missile shots, which just isn't enough by itself. You want Logan to be giving you mobile Melta and S9 Missiles.
Dark Eldar
Webway Portal. being able to start off the board and arrive from the center is a huge deal. Having abundant Fleet, Beast, and Jump Pack units in combination with this is basically what drives the list. And squads of 20 guys with FNP? That's just gravy on the cake. Mobility comes from the ability to place the Portal anywhere they want- when you can arrive from the center of the board, you are effectively halving the distances you have to cover over the course of the game. Protection comes from cheap bodies with FNP and the ability to get charges straight out of the Portal. Control is likewise from their ability to dictate where the charges happen and when and where the opponent is allowed to engage them.
So let's look at Goatboy's thoughts on the subject and see where he goes wrong in analyzing things:
1. Ease of getting that cover save.
Good mech lists should be able to create their own cover saves by layering chassis- the so-called "parking lot" or "Rhino wall." Even with a 4+ all the time, infantry will find themselves getting chipped away at, whereas vehicles are immune to a large number of weapons in the game, which is one reason they're so tough.
2. Capturing more than one objective.
If your opponent lets you do this, he is an idiot. Assaults, tank shock, and simple shooting casualties should make spreading a squad 12" (the minimum distance between objectives) awkward at best and fatal at worst.
3. Utilizing more USRs
While it's true units tend to have more rules than vehicles, most every rule that infantry can have, vehicles can have as well. Stealth is pointed out as one advantage, but there are vehicles that can get Stealth as well. I don't really understand this inclusion.
4. Ignoring heavy weapons
Since most all of the foot lists he mentions are MEQ lists, this one seems rather nonsensical. Your cover save mitigates some of this, but that's point #1 already.
5. Creating traps
Basically, he means baiting the enemy into poor charges, etc? But with superior mobility and more throwaway units (the transports themselves), mech is infinitely better at this.
6. Confusing the opponent
Certainly underestimating your opponent is a danger. However, relying on your opponent to play poorly is a bad idea- and assuming that someone is a bad general just because their list isn't ideal is definitely playing poorly. You might as well include "Opponents underestimating you because they think you're just netlisting" as an advantage of mech if you're going to do this.
7. Challenging to play
Necrons are hard to win with, too, that doesn't count as an advantage. Everyone tends to think their army is "challenging to play" or "skill-intensive" because saying so reflects well on them and excuses failures. This isn't even a real argument.
Green Tide list
Foot Orks are bad because they have to spread across the board (allowing the enemy to refused flank/defeat in detail them) and because they lack good ways to deal with transports. Sorry, I'll just shoot your Lootas to death and laugh because you have no other way to hurt me. Also, Ghaz and the Mad Doc? Seriously? You know that TLOS means that it's going to be virtually impossible to stop the Doc from doing stupid things, right? Enjoy chasing my Rhino around the rest of the game!
Mobility: None to speak of. Short-range guns + BS2 + only Fleet once means you're slow as molasses.
Protection: A bunch of bodies shielding your Rokkits and Klaws is actually pretty good. Needs a KFF, though.
Control: The opposite of this. The enemy is always going to decide where and how they fight you.
Smurf Horde
Derp. So it's one strong countercharge unit, a useless character, and overcosted fire support? What does this list do when I just sit on the objectives turn 2 and laugh at it? How can it ever do anything but tie a Capture and Control mission? What does it do against a Land Raider? (Remember, since it can't push Melta forward, by the time you can use it, my Land Raider is already in your lines and tearing shit up.)
Mobility: If you move, none of your guns work.
Protection: Still just Marines in cover, sorry.
Control: Good countercharge helps, but it's not enough to redeem the list.
Dark Eldar
Good try, but why only one squad of Beastmasters? They're the best thing to come out of a Portal. Also, why no good ways to deliver the Portal? You want to move forward and put it down T1 so that guys can come out of it T2. Hanging with a static foot squad is not a good way to do that. It needs more ways to deal with heavy infantry and tanks and wait 20 Khymerae what the hell?
Mobility: Okayish. You're not really using the Portal to its full advantage, but it's reasonably flexible, at least.
Protection: Sorta. FNP in cover is annoying and you can jump out to surprise folks.
Control: Not really. No screening units to protect things, short engagement ranges.
Space Wolves
This perhaps the closest thing to a functional list among his choices, but it's severely lacking in firepower. And what the hell is that Wolf Priest doing in there? This isn't going to get the charge on anything, take another Lightning dude instead. It also needs some Long Fangs, but aside from that it's pretty decent.
Mobility: Nothing wrong here.
Protection: This is sort of the weakness of Loganwing, but he didn't make it any worse than it has to be.
Control: He's got Chainfists in there to discourage charges and all, so doing more or less fine.
Although 5th Edition is certainly a time when mechanized lists are waxing strong, foot lists can be viable. However, this does not mean all foot lists are workable (just like not all mechanised lists are viable)- only the newer books have the tools to reasonably do so, and not even all of those. Foot lists have to be built with all the same concerns (firepower, mobility, flexibility, etc) as mech lists do- they get no special passes in that regard.
