I think the problem with siege is... well, it's boring. I won't mention the awkward melee and invincible cav because that is a general combat problem we all already despise.
But siege is repetitive. The flags are there, and they must be captured or defended. So we all charge flags, capturing or defending. We can't ignore them or we lose stars. Then we lose the game.
I preferred the old way. Sure, I didn't like the running as an attacker or the dead waiting as a defender, but I did like choosing our own strategies. Do we hold the wall or pull back to a choke hold? Are there enough men covering such and such point (and yeah, I blamed everyone else if there wasn't). But there seemed to be spoken and unspoken agreements in place. Or none at all, I which we lost quickly.
But all those flags take away the renowned sandbox feel of Mount and Blade. At least Deathmatch, chaotic and annoying as it is, doesn't tell you where and who and when to attack.
So, essentially, most people despise it. Bannerlord is like the Star Wars prequels: they took away what made it cool, twisted it into something we barely recognize, yet we all joined in out of respect to the original, and really hope it will improve.
But until Taleworlds admit their experiment went wrong, we'll just have to wait for the mods.