A big problem with cav is the relative low risk attached to attack an inf, when compared vice-versa.
If the cav gets reared, it's difficult to get punished. There's a small opportunity window for inf and ranged to deal damage, plus the height and the stature of the horse blocking the rider makes it hard for inf to get a hit in. The inf rearing the cav can reliably punish the cav, if no one is around. But if it's a spear, you can only deal around 25-30 damage. That is nothing, compared to the cav that can do a stab or swing and deal 40+ after a double-tap W.
The only good way for an inf to punish a cav is with a swingable 2h polearm:
-It is long enough to have a chance of rearing the cav with a spear.
-It can follow-up with an overhead/side swing, that can decently reach the cav and deal proper damage.
However, 2h swingable polearms are scarce in the current perk system. Only the Empire (menavlion) and the Khuzait (glaive) have one, with the latter not even giving it to their infantry!
As an inf, you can make at most 1 mistake, before you die to a cav. A cav can make 3, or 4. Allowing infantry to punish cavalry better will go a long way. And they already have their specialized tool for it: spears. They're just not up to par against them right now that is partly the cause for this discussion.