Well I already put forward some pretty objective statements of why I didn't think it was fun.For you. That basically boils down your points. Bannerlord isn't a perfect game, I'm under no delusions about that, but because you don't find it fun, does not make that game a bad one. I don't find Civ fun, I'm never going to call it a bad game. Just because the game isn't fun for you doesn't mean that Bannerlord is a bad game.
Explain what makes something a bad or good, fun or unfun game, then? Would you not call Atari E.T. a bad game?
To me, it is a reasonable statement that an RPG that has bad roleplaying is a bad game. A grand strat that has bad politics and bad AI is a bad game. A slasher with a bad damage model is a bad game, and a tactics game with only 2 viable tactics is a bad game. If it doesn't accomplish the point of the genre/s it's part of, it isn't good.
You can push the subjectivity angle all you want, but at the end of the day if we don't try and create some sort of statement on what constitutes good or bad, then you can also never call anything good or bad, and never critique anything either.
A "game" at its core is being challenged, and overcoming that challenge either through skill or smart decisions. In Bannerlord, a lot of the time your decisions are obvious or don't matter - vote for choice A or choice B? doesn't matter, the lords all already voted one way - and your skill has little impact - it's a 500v500 man battle with only two viable tactics, and you'll get taken down by a handful of stray arrows if you try to fight. You spend a lot of time just... running around the map, clicking "recruit all", doing fetch quests; going through motions that don't require neuron activation or reflex action, which is what a good game does.
Nearly every feature is either unimplemented, incomplete, horribly imbalanced or bugged. So, how can you justify saying "it's hard to argue that it's a bad game"? The opposite is true, it's VERY easy to argue that this is a bad game. Good fundamentals, but lacking what makes games fun.