Not your parent commenter but I love Firefox more after discovering that you can't even customize the toolbar buttons in Brave. That's such a basic functionality that I'd taken for granted, until I tried to move out of Firefox for a brief time.

Lack of sufficient customization and lack of extensions I want. The customization is a big deal because I dislike the Chromium UI and want to be able to fix the worst of it. My dislike of the UI is also a source of grumbling from me about modern Firefox, which has picked up a lot of Chromium and which is also less customizable than it used to be, but I can still fix a lot.

I also want to be able to use the same browser at work as at home, and my workplace banned the use of Brave when it started including a VPN.