"cavalry counters archers" is only a legitimate thing to say when a GROUP of cavalry encounters a GROUP of archers in a battle. So yeah, it comes down to formations and how units behave when in masses. There are no magical (+50% damage against archers) bonuses assigned to units like in age of empires.
Combat units act dramatically different when they are grouped versus in case of a 1 on 1 in some street (how it mostly is in bannerlord mp).
A horse is not an easy thing to maneuver, if it does not have armor it is fragile, and you cannot micro manage our movements on a horse when it is at high speed. An armoured lance charge works wonders when done in formation against a MASS of enemies, but it is hardly effective when done by a single horseman with the aim of killing a single enemy.
To put it into perspective, lets say you have a great bombard. That bombard can tear down entire walls and kill 30+ soldiers in one shot. However if you tried to aim that same mortar towards ONE specific guy who is walking around the streets in the city you are besiegeing, you are not going to get a satisfactory result, but this will not mean the artillery is not a good anti-infantry asset. Or how one musketeer trying to shoot one guy in the distance doesnt succeed while a regiment of line infantry can kill a good 20+ enemies in one volley.
also most of the time the players in this game the skill gap is massive. So yes balance issues do exist but also if you are an average casual player against a proper clan member you are going to get messed up pretty hard no matter what your class is. Doesn't matter if he is a peasant with a butter knife and you a cataphract he will dismount you and proceed to kick you around and continously stab you in the face while circling around you. The game need a good rank system. But before that it somehow need to come back to life, either with good mods announcements or major updates, or private owned servers. The way things are, no balancing is any important because what are you balancing for if you dont have people playing.