I'm one of them. I switched to Brave first, and have settled on Vivaldi going forward. Why? Because Firefox was increasingly problematic to use. Things like background blur on Google Meet didn't work.
Yes, I realize it was probably Google doing Google things to hurt Firefox, but day-to-day, I need a browser that works. So switching to a Chromium-based browser that had things like ad-block and other features I consider important was the best solution.