There, much more civilized and productive Mr Rex. Let me address those points as they stand in EB2 (discussing M2TW would not be interesting, this is a EB2 thread after all).
that made every cavalry charge completely worthless unless on a flat plain, head on with a long time to form a straight line.
This is something they have improved in EB2. As long as they are a minimum distance away cavalry units will receive their charge bonus. Being in a straight line makes it more effective as you have more guys hitting at the same time but not indispensable. And terrain is quite generous, I've managed to break phalanxes with flank charges while charging through woods on a slight uphill slope.
Not broken because of some realistic unit cohesion physics, but because of an unrealistic constipation of every single man that makes them stop and move as slow as possible everytime a single soldier of the unit is engaged.
Again something they have improved in EB2, with the exception of phalanxes. As it stands they are the only type of unit that behaves in a glitchy manner because of a problem with their unit leader and standard bearer (but they are supposedly working on it)
This constipation also applies to attack animations, which means you end up with absurd cases where a single unit of peasant can take down an army of Knights coming out of the tower. Because they're stuck in gelatin, their trajectory of climbing a tower to a wall being too complex for the engine to handle.
This I disagree with. Maybe it happened at launch (but that was 6 years ago, not going to remember that anymore), but it has been improved in subsequent patches of the vanilla game.
Medieval had several custom animations for one soldier, needing two soldiers to be locked into it. Or perhaps it's because of the computing power new animations required, that led to a bad optimization where soldiers AI slows down to allow the software to handle it.
The death animation was not added in empire. It's bullshit. The problem was already in Medieval 2.
You are mistaken here. While it is true that combat animation were slower and more complex than in RTW, they didn't lock 2 soldiers in a choreography. Multiple soldiers could still engage a single one and take him down faster, none of the single guard unit taking down endless militia bullshit because they can't be attacked simultaneously that started with Empire.