I think it's okay to generate alternative text for images with AI. Preferably locally. But please PLEASE at least read what was generated.
Oftentimes a small detail is wrong and completely changes the meaning. Sometimes it's completely wrong. Or if you post screenshots of games or stuff change "a man", "a woman" or "a group of people" with the actual names.
I know alternative text is time consuming sometimes, but it's important for a large portion of users.
So please take the time to read what was generated and correct mistakes or add nuances. It only takes a small amount of extra time but helps a lot.