Most people probably assume platformers can't have much depth, beyond Mario with lots of lock-and-key sections added (i.e. Metroid). People realize that platformers can get harder by being faster or requiring closer tolerances, but that doesn't add any more depth.
Well, N proves platformers can have more depth, by relying more heavily on momentum, by using a more complex jump arc, by using "balance" (i.e. different slope angles result in qualitatively different behavior), and by reducing the number of threats the player faces (so they can "drill" and become very precise at evading them).
Granted, all this demands a lot of practice time. However, it's not merely "speed it way up without adding any extra depth".