I honestly think modern indie platformers like Celeste are better platformers than what Nintendo has been doing.
I've been waiting to play DKTF and NSMBU for years. People have said shit like," NSMBU is the best 2D Mario since Mario World" "Tropical Freeze is one of the best 2D platformers of all time!" But both are just okay in the case of NSMBU and just good in the case of DKCTF.
It depends on what you're looking for in a game.
NSMBU offers decent and fair platforming challenges and there's plenty of cool Gizmo's to toy around with. I enjoy games like Celeste too but they are less accessible as indies either make their games very difficult or more complex (rather too confusing) towards the end. Nintendo's games often offer much more variety in themes and challenges packed into a single game. Until Tezuka retires Nintendo will probably keep making 2D Mario games using the same basic principles as Super Mario World. And in that sense I would say NSMBU is the best in the New Super Mario Bros. series. However, this game isn't aimed at hardcore players but families and kids who want to play Super Mario together. So you won't find it real challenging as a veteran gamer.
DKCTF is a different beast all together. GameXplain pretty much nails why it is so good. But for me it was just the fact that the entire world felt connected and that David Wise soundtrack combined with some awesome vertical platforming.
Each level is unique in that game, which is not the case in NSMBU.
I enjoyed Celeste but it felt more like a trial and error puzzle game than a platform game. DKCTF in that sense feels more like an action game with all the events and variety (but of the good kind in my book).