If someone gives you a gift you think is broken, you ask them to empower you to help mend it. And if they offer to get it mended, you at least offer to go with them.
That said, yes accessibility should be prioritized.
Nothing in that list was "negative". They were all dry factual statements. Tone policing people for being "negative" when they're not is in and of itself quite a negative thing.
If you don't want to be considered a jerk, in polite company you would say something like "This is a nice project. I have a few suggestions and bugs regarding accessibility:"