There are two ideals of what a platform game is.

The first is the ideal embodied by games like Mario 64, Ori and the Blind Forest or the (unfortunately short lived) 'new' Prince of Persia. That ideal is that platform games should be free flowing and give the player a sense of creativity and freedom. Any given location you're meant to go to can be reached in a plethora of different ways and the way that you reach that location is up to your own sense of flow as to how you're going to achieve your goals. You can get up to a hypothetical cliff by wall jumping, doing a back flip, bouncing off some enemies or shooting yourself out of a cannon. Up to you.

The second ideal is the ideal embodied by games such as Super Meat Boy, which hold that there's only one specific way to advance the game and anything else has to result in failure. In these kinds of platformers, the basic task of the game is to reproduce the button inputs and timing that the game designer laid out for success. Platforming sections in these cases are essentially complicated quick time events, where mistiming a jump or dash results in instant failure. You can get up to a cliff by bouncing off a cloud, jumping over the spikes and dashing diagonally up to latch onto a cliff edge and any deviation from that exact sequence means that you die and start again.

Celeste starts out in the first few levels (ignoring the hard-mode 'B-Sides') with the first ideal and then steadily moves towards the second. The first two levels flow easily together, but by the latter half of the game (particularly in the unacceptably long final level), you are going to be expected to do pixel-perfect platforming challenges to send this thing home. The game has some built-in cheats if you get tired of it (and you will), but if you just want to cheat through a game why not just watch it on Youtube?

If you're someone who thought Meat Boy was a genuinely good game, then this thing will supply more of that. It's certainly hard and 100%ing all of the B-Side challenges is certainly well beyond the scope of my patience.

But if you're someone that plays platform games because you enjoy the feeling of movement and freedom, then this is not a good platform game by any stretch of the imagination.