There's plenty of valid criticism against Kingmaker. Kingdom management, trash mobs sure, encounter and dungeon design could have been better, no doubt about it.
But overall as a package, it's fucking incredible and it vastly outshines its rough edges. Pure combatfag heaven.
So I always just assume people who don't like it are either storyfags or they got filtered by the difficulty.
Cause whatever complaints you do have, I don't think it trumps the character building, combat and the fact that it doesn't give a single fuck to hold your hand in any way.
It's not really being a storyfag IMO, it's wanting a balance. Kingmaker is amazing for combatfags and people who obsess over mechanics, as you say. However if you want a balance of that along with story, exploration, freedom, etc. then it starts going down your top RPG list relatively quickly. Don't get me wrong, I enjoyed it and finished it, and I wouldn't even say it was hard (on "challenging") until the very end. However I wouldn't put it in my top 20 or anything because it was all combatfag, with zero polyamory.