Have you seen the new Nova theme? It’s horrible, especially with vertical tabs.

I took the screenshot with the nova theme enabled. That’s what it looks like. It’s a nothingburger.

Also with standard tabs. I mean it probably won't distub someone already conditioned by abhorrent MacOS design... but the lack of visual boundaries of tabs (independent controls), the terrible vertically uncentered close buttons, the whole thing is a visual Chernobyl meltdown... Mozilla working hard to kill Firefox.

edit: just checked, and the most disgusting thing the extra internal horizontal top border of the text contents of the tab titles got removed. Still ugly, but nor instant Alt+F4... now I can bear it until I find about:config.