Personally I like how fast the renown is earned. Seriously, it means a player can go at their own pace and enjoy the game for what they love to do, instead of feeling they are doing a task or a chore.
I also can see that some players feel they dom't have anything else to do or their goal is gone when they reach max level so I agree with the idea of giving something after level 100. Maybe bñue doubloons, that would be fantastic since we are now gwtting doubloon sinks and for some people it would be amazing to get the previous cosmetic sets. 5 doubloons per additional level past 100 would be nice.
I mean, I already am playing another game (at the same time, just switching every now and then) that does exactly this, when you finish their battle pass you earn currency per additional level. In that game you don't miss any reward if you stop playing after reaching max level, but if you keep playing you get some extra currency for other stuff. Sea of Thieves could do something similar.