As someone who almost compulsively changes browsers every so often with the mistaken belief that "there's gotta be something better" and has swung by Firefox on multiple occasions, it has never offered me any compelling reason to stick with it beyond not being Chrome.

Zen came close, but also didn't stick.

Containers seemed nice at first but my personal usage of them devolved into an over abundance of containers to isolate everything from one another (my fault, though).

On the other hand, I've had various small nits here and there that always eventually push me back towards a chromium browser.

But hey, I'm a believer in not holding on to my decisions so long that they become assumptions, so off I go to install Firefox and give it a 4th whirl since 2010.

Try Tree Style Tabs.

That's gotten me married to Firefox. The hierarchical vertical tab management makes research and general web browsing far more efficient and productive. It also helps me know which tabs I can close when I'm done.