I actually genuinely like spears. They're not too difficult to use for the player and they can do a lot of damage pretty quickly. The problem is that the AI is awful at using spears, they can't be used in close quarters, and they can't be used in a tight formation. Part of the reason pikes and spears were so effective on the battlefield was because even in close distance, they still hurt, and more spears at once meant they hurt even more. Spearmen and pikes in tight formation were almost impenetrable by inf and cav because a wall of spikes meant a lot of pain, and shields were difficult to penetrate. The collision detection on weapons is also screwed up right now. Spears can't thrust with someone directly behind you right now, and other weapons can't slash, so spears are useless in shield wall, line, square, and circle formation, being most effective in loose formation. In fact, the most effective formation against cavalry right now, is loose formation.
So my patented solution is thus: Get rid of the limited collision detection on spears. If someone thrusts with a spear, thrust all the way. Maybe lower the damage a tiny bit, but right now, spears can't be used in formation, so that's the first step. More effectiveness along the whole range of the spear, and let units in formation use their spears. This lets them use spears against cav and inf right next to them. That simple.
Second, make the default behavior less clustery. Right now, infantry vs infantry fights are mosh pits. They'll get in each other's faces with no self preservation. In warband they would at least back up sometimes, but here there's nothing like that.
Third, let us order them to use specific weapons. The AI at least defaults to polearms against cavalry, but against inf they never use spears for the reasons above. Fixing those would then mean we'd need to be able to order them to use it.
Fourth, make the perk that pushes blocking units back with a polearm default behavior. This might be an unpopular change, but I honestly think it would be a good idea. It would make spears more useful in infantry fights and would give cavalry charges more Oomph. As part of this, they need to give units MASS. Otherwise there's no point, because cav can already just charge in with impunity and disrupt formations. Mass will probably be implemented eventually anyway, but this makes it even more necessary. I don't know if it actually works, but frankly I don't care, it would be cool.
Hope you enjoyed my wall of text. I really do like using spears. They have a lot of problems, but they're still quite effective if you know how to use them right. But not in the AI's hands. They could be so much more than they are now. I know it's early access so everything's bound to change, but I hope they take some of this into account.
TLDR; 1. Make spear effective at whole range and make the collision from behind more forgiving.
2. More space between inf while fighting, less mosh pits.
3. Order AI to use Pokey stick
4. Let polearms push blockers/formations back all the time.