Eh... I think it's debatable. From a player perspective, it's a good mechanic to uniform the cultures in your realm if it's big enough, since a lord will spread their culture in their territory, and thus make things a bit easier (less popularity problems, rebellions, also causes less troubles if you export the game in EU4). It also adds some variety/chaos by allowing cultural & religious changes without necessarily only relying on brute force.
On the other hand, it's true the AI tends to do some wacky stuff from time to time, and even if I personally really enjoy when there's a sudden change in the "normal" course of history (ashkenazi jewish France sounds pretty fun), I'll agree that some decisions are poorly made by the AI at times.
Arthur
![[Arthur-PDX]](https://forum.paradoxplaza.com/forum/styles/paradox/owneditems/avatars/dev/s/PDX.png){kind=avatar}