Yes, and expensive. This is often overlooked when people just say don't worry it's FOSS. The enshitification happens slowly, and by the time there is outrage about how bad it becomes the last non intrusive fork might be several years old and take even more work to modernize. I'm not giving up all hope, but you are correct, it would be a very ambitious community undertaking to keep such a thing competitive with the plethora of evil browsers out there.
Vivaldi, although it's extremely nice tab management system and unique features, isn't open source. But probably the better chromium browser of the owns you mentioned.
There are a plethora of sources out there of good reasons not to use these browsers. But seriously, Firefox is an excellent browser, treat yourself to better privacy 🦊