Out of curiosity, what type of levels do you like in Mario Maker? Particularly, how difficult do you like them?
I'd say anywhere from 1-20% makes for a good challenge. Under one is usually a troll level and kind of annoying. "Don't press/speed run" levels are cool, but get old.
And, of course, I hope Nintendo stops tampering with the hardest levels by automatically deleting them. I had several levels removed in the first game, which I was NOT happy with.