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.
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.
I've tried all kinds of tab management things (they're usually a motivation for trying a new browser that supposedly offers a better way) and nothing ever sticks out for me.
Oh and of course focus. Mozilla has lacked focus for almost a decade now with all the random products and initiatives they launch.