If you want to talk physics:
Every one of those flying shields is a dead infantryman.
Seems reasonable. Btw if that makes sense then not only do I not mind but I prefer it. I like the idea that I win a battlefield fairly and that my opponents gave their best before going down.
Now, there has to be some technique or some very basic tactic of handling some damage to cavalry. These horses can trample over people and send organs flying in different directions, especially when it's a big horse going at a high speed. But there has to be some countermeasure historically speaking. I can not imagine that simply having horses is like an ace card promising 0 casualties. btw you are more than welcome to critique the physics and natural logic of the combat. Constructive criticism means a better game for all of us.
But horses going at relatively low speed will definitely feel a spear, I think. So the difference dictated by speed and energy is a big one. If the spears were stuck to the ground pointed at the horses and not that fragile I assume some horses would get pierced or at least trip somewhat.
I just want death, that is all. And I want a battle where people aren't superheroes but actual people that get injured and die very easily, like in real life. Not endless stamina.