Hiya :3
I had the exact same problem yesterday. I'm on a Macbook Air M1 and although the controller works with my Mac, Celeste seems to reject it.
I just got my XBox Wireless Controller to replace my Logitech F710, which worked fine with Celeste (on the D-Input setting).
After tinkering around a bit I came across this YouTube-Video where the person used an App called "Enjoyable". It's a mac app which lets you map keyboard inputs on a controller. So what i did was just remapping the keyboard controls of Celeste on my XBox Controller with Enjoyable and saving the Profile. Now my Mac thinks the XBox controller is a keyboard and i can play Celeste with my Controller no problem.
Here's how i configured my keyboard settings in Celeste:
This is the standard Controller-Layout for Celeste, I recommend just emulating that in the Enjoyable-Software:
I hope I could help you with this. Sadly there seems to be no other way to get this to work correctly with the XBox Controller atm.