I found it's lack of support for native functionality in MacOS too irritating (eg doesn't support system wide autocomplete - so my @@ shortcut that puts my email address in doesn't work in FF - I know I could put it in again in FF but it's annoying it just doesn't work) so I went back to Chrome in the end.

I was using Edge for a while but the absolute car crash their UI has become - and can't be configured - sent me running screaming for the hills.

Edit - and don't get me started on the massive slowdowns once I have more than a handful of tabs open.

My biggest complaint with Firefox on macOS is the lack of support for native picture-in-picture. They implement their own version that doesn’t stay visible when you swap between the virtual desktops; won’t overlay on top of full screen applications; and can’t be moved across monitors (iirc) either.

Now that's weird as PIP in FF always worked fine for me - including swapping between desktops and full screen. In fact I thought PIP in Chrome wasn't as well implemented as took several more clicks to activate.

Can't comment about monitors as I don't use a multi monitor setup on my Mac.

Your experience made me curious, I had to check and it looks like you're right – it does work between desktops and full screens. In fact it even works between monitors. Don't know why I thought it was in such a bad state, but I'm glad you replied. Cheers!