pro-AI for starters, lots of people aren't happy with that. (this is related to the AI, but started long before then: ) their insistence on focusing on anything else but the actual browser, Firefox also occasionally changes (privacy related) settings after upgrade (Edit: as reported by users online) or when they installed extensions remotely to people's browsers as part of some kind of promo (I believe it was Mr. Robot?).

There might be more, but this is what I can think of from the top of my head.

Edit: typos