I like that there's a lot of content for those who want more of it. That's how you should go on about all games: If you don't love the mechanics and style, just finish the main game.
I'm replaying Super Meat Boy these days, played it ages ago but don't really remember much. And wow, in my opinion Celeste is like, ten levels above it. I am enjoying Super Meat Boy decently enough, but Celeste's visuals and music is so mature and elegant that it feels like a different medium. The plot and presentation is obviously on a whole different level as well. And what I love about Celeste is how coherent it is, that it often feels more like a metroidvania than just random challenging rooms after another. And then the controls of course, some of the best and tightest ever in Celeste, while you're flirping around like crazy in Super Meat Boy. I wouldn't call them bad in SMB, they're quite flexible compared to a lot of other stuff in the genre, but again, the amazing thing about Celeste is how many moves there are, how many special techniques, and how all of it is so very adjustable and flexible. A millisecond difference, and your angle will change! That's what I love about it.
This really just turned into a random rant, but what I'm trying to say that for me, Celeste is in a league of its own even compared to other highly rated platformers. If it had a bit more level/environmental variety, it would be clearly above Super Mario Bros 3 and World for me. It's that special.