Wow, you beat DKC: TF hard mode, TC?
I'm more concerned with there being varying types of difficulty. As others have alluded to, challenges may include: puzzles, platforming segments, mini games, combat based, simple fetch quests, and more.
Players should be able to skip what hey don't like and at least approach the minimum amount of quills/pagies. Those who dig deeper and expand areas should find more challenging segments. I'd personally like a difficult final boss. I enjoyed that Grunty took a few goes to beat