(easiest to just skip inf entierly, and might make sense in a near-future desert scenario (modern armies use mostly vehicles in open terrain), but dont want to give it up just yet).
I say this is spot on (save the mostly vehicles part, but I come back to that). Vehicles can always look believable with minimal or no animation, and you can hide the missing animation easely with rather simple effects like kicked up dirt or engine smoke.
infantry without animation looks off.... or creepy, if that fits your background. Some kind of mechanized zombies floating above the ground with very simple attack effects representing how they don't even have to move their arms to do damage for example.
Not really your average everyday infantry, but might work in the right context.
Given it is a near-future background, why not come up with smaller drones that take human infantrys place on the battlefield? Not 100% believable in near-future scenario given all futurologists tend to agree that drones will first take on support roles alongside the infantry before making the human completly redundant on the battlefield (if that ever happens).
But maybe in your game something happened that speed up this process.
Result would be infantry-like units, that would look more like small vehicles or air units than human drones. Given how much todays engineers struggle with basic two legged movement, and how unstable even multi-legged drones often walk, while small tracked drones are getting pretty good at navigating pretty uneven rubble, this is more fitting to a near-future drone than a humoid form.
Also, the humanoid form might not be that desirable at all, unless we build bots that have more of a social than fighting function. Even then, the uncanny vally will most probably dictate that humanoid bots either look completly like humans, flesh and skin and all, or keep a healthy distance from looking to human.
Those bots in "I, Robot" really looked off. Good for making the bat bots look creepy, bad for the good bot looking sympathic. Should have leaved the face away and gone with a simple display, or faceplate. Emotions could have been symbolized rather than shown with a humanoid face so completly unfitting to the rest of the bot.
As to the "use mostly vehicles"... yes, and no. Its true that infantry in modern wars are extremly vulnerable in open terrain thanks to modern weapons introduced in WW1.
At the same time, vehicles actually are even more vulnerable thanks to the modern antitank weapons pioneered in WW2 and developed further in the cold war. Even a modern composite armoured tank is extremly vulnerable to precision airstrikes, modern guided artillery, or a lone RPG that is well positioned.
Even today, combined arms warfare is mandated in all kind of terrain. Ground vehicles without air support quickly run in to troubles as mobile ground based AA fire often is not enough, and a supportive airstrike can be pretty effective in case of a stalemate.
In the same tune, tanks always bring their infantry along. To take the lead should the fighting move into urban or other cramped terrain... but also to dismount and spot and maybe also take out enemy infantry well hidden, and posing a potential threat to the tanks that might get shot into their sides oder backsides by them.
Modern tanks have a huge array of sensors to spot even infantry sized targets, but as far as I am aware still in a rather narrow sector. Dismounted infantry units will maybe not be able to spot threats as far as a tank, but certainly they will be able to spot infantry targets in a wider sector up close. And they can do so while keeping a low enough profile to not be spotted themselves, which is almost impossible to do even for an armoured car unless this armoured car is just laying in wait and is camouflaged up.
What has changed is that you hardly will see infantry units on the battlefield without their own transport, often an armoured vehicle with its own breed of support weapon. Mechanized infantry has supplanted all the footsloggers in almost all roles in most modern armies, as their utility is just far greater than a bigger mass of soldiers moving about at a mere 4 km/h, or having to rely on big lorries organized into their own units to move around on the battlefield.
If anything, the infantry soldier of the future will be way better equipped, is far more mobile, but fewer in number. But he still has a place in ALL kind of engagements, because vehicles still cannot deal well with well dug in enemy infantry even outside of cities. As long as precision airstrikes often lack the precision of a well executed infantry attack (were every shot could potentially be made at a distance were friend could be told from foe, instead of through the blurry view of a night vision cam at max zoom), and tanks still have weakspots exploitable by infantry weapons (which will most probably be the case forever), infantry will have a place on the battlefield. Well trained infantry is hard to spot, hard to hit (try hitting an infantry man that has gone to ground with a direct fire weapon... sure, you can saturate the area, or use HE.... still, a pretty darn small target), and can use a wide variaty of weapons lethal to all targets. They are ideal to navigate areas made for humans like cities, and will alwas have a huge advantage there. They are light, and flexible in some harsh terrain where tanks would get stuck instantly.
Last but not least, they are cheap. Even as a well equipped and trained mechanized infantry unit, they will cost less than a modern battle tank even with their AFV.
Of course they cannot blow up things as spectacularly as a tank from afar. And if they end up as target for the tank from afar in their AFV, they will have a bad time. But they can do many things a tank can't, at a fraction of the price, save from going 1-vs-1 in a straight vehicle battle against the tank. If they can use their strengths while making sure the tank cannot use his, they have a good chance of disabling the tank anyway.
