I donate to the Mozilla foundation, and I love Firefox a ton. But I can’t seem to like the UI by installing a theme, and when I change it to look better the browser slows to a crawl. Does it really matter all that much if I use Chromium?
P.S. To the people from my last post regarding something similar, Firefox was too slow, I’m sorry, but I use Vivaldi instead of Brave because Brendon Eich can suck my dick.
Out of interest what part of the UI don’t you like? You can drag and drop pretty much any button and component where ever you want and you can use the Firefox colours website to apply any colour scheme you want. This is all core browser features so no performance affects.
What is it that a theme is then adding?
Not OP, but I also prefer Vivaldi over Firefox. My reason may not be the same as OP’s, but for the sake of discussion, here it is. I simply can’t stand having tabs on top of my screen, and I’ll go to great lengths to have them on the bottom. On my private computer, I used to use Firefox with Tab Mix Plus, until Mozilla killed support for such extensions. I later managed to get the tabs to the bottom via custom CSS for Firefox, but every few releases the CSS stopped working and had to be recreated from scratch. So, I switched to Vivaldi. On my work PC, where only Edge and Chrome are allowed, my workaround is to work in separate windows instead of tabs, but that tends to get a little messy.