Brave is probably a better option if you want to "drop out". Unlike Firefox, it is not a dying browser, and it's monthly active users are increasing: https://brave.com/36m-mau/. They do have a cryptocurrency for relatively privacy-respecting ads thing (Brave Rewards), but you can easily opt out of that. (Also, we should not be puritans about this, developers have to eat too)
It is still based on Chromium. But that's probably more of a plus for the typical user who cares more about websites working correctly than browser diversity.
[1]: https://www.investopedia.com/articles/investing/041315/how-m...