Same here. I stopped running cav army because it gets boring for horse archer and stupid for melee cav. I just use an army of spears and javelins and they worked really well. I start to notice the reason why is because troops are more likely to attack with longer-reaching weapons and the AI cav keeps running into spears and spear braces without fail.
Plus, they are garbage at actually countering enemy cavs, so the cavalry AI needs to be a lot better. Maybe make it so the AI actually utilizes charging cav and melee troops together and reposition when, say a specific percentage of casulties was sustained, so they switch strategy or something.