How is performance not great? About 2-3 years ago, they made a huge amount of improvements to Firefox performance, to the point where it's plenty fast. I have it set as my default browser and have actually disabled Chrome so Firefox is used for everything.

Performance is more than sufficient for me, and I've done a mix of playing browser games and regular browsing and haven't had any issues. And this isn't on a flagship phone or anything, it's just a Moto G Power. I don't really notice any performance issues, and it's probably actually faster than Chrome on average because my ad blocker means i have to render far less stuff.