Heres some easy ways to make feudalism and the civic for it more worth it.
Gates can be built in vassals territory, if the vassal gains independence the gates belong to them if they win.
Vassals now give half the taxes a tributary does (Without the feudal civic)
Feudalism civic in addition to the power relations now makes vassals pay the same amount in taxes a tributary would (and maybe give a bonus to tributary income so you have some reason to do that too)
Easy band aid at least, until the AI can be fixed.
Another idea is that instead of increasing vassal tax income the feudalism civic would make vassals give bonus fleet capacity and unity based on the size and economy/tech level/number of pops of the vassal.
Gates can be built in vassals territory, if the vassal gains independence the gates belong to them if they win.
Vassals now give half the taxes a tributary does (Without the feudal civic)
Feudalism civic in addition to the power relations now makes vassals pay the same amount in taxes a tributary would (and maybe give a bonus to tributary income so you have some reason to do that too)
Easy band aid at least, until the AI can be fixed.
Another idea is that instead of increasing vassal tax income the feudalism civic would make vassals give bonus fleet capacity and unity based on the size and economy/tech level/number of pops of the vassal.