I agree. I'm not a Firefox fanboy. It has literally run better for me than Chrome for a few years now.
I switched to Firefox recently and many sites don't quite work: for example the pull request popup menu on GitHub appears off screen so can't be clicked on; the "new post" panel in Discourse is obstructed by the keyboard; FastMail alert box buttons don't work, and many other such annoyances.
It can be used as a main browser but it does have problems. I wouldn't bother with it if it wasn't for the manifest v3 situation
The same workflow works fine in Chrome.
You seem to be talking about the mobile version?