It depends. If it's just for the sake of plugging AI because it's cool and trendy, fuck no.

If it's to improve privacy, accessibility and minimize our dependency on big tech, then I think it's a good idea.

A good example of AI in Firefox is the Translate feature (Project Bergamot). It works entirely locally, but relies on trained models to provide translation on-demand, without having Google, etc as the middle-man, and Mozilla has no idea what you translates, just which language model(s) you downloaded.

Another example is local alt-text generation for images, which also requires a trained model. Again, works entirely locally, and provide some accessibility to users with a vision impairment when an image doesn't provide caption.