I also use Firefox because it allows more customization.

For example, every major browser nowadays not only supports tabbed browsing but enforces it.

I think tabbed browsing is misdevelopment of UX because I need to handle window management on the OS and browser level. I'm using the tabbing feature in sway/i3 so every application has tabs not only browsers and they all act in the same way.

I know that not many people think this way. But that's the whole point. We should be able to tailor software to our needs.