Does CK3 stay enjoyable after the challenge is gone?

I’ve been thinking about getting into CK3, but I’ve heard from some people that the game doesn’t pose much of a challenge after a while. If so, does the enjoyment drop drastically at that point, or is it still fun to play?

What are the best ways to make the game more challenging? Mods? DLC?

Also, how long do you think it will take before the average person gets to that point when there's little to no challenge?

Thanks!