Tabs are just one example, albeit an example I care about a lot, but this kind of thing happens with Firefox all the time in general too. A new version comes out, some random behavior has changed, and either you suck it up, or you go play whack-a-mole in the minefield of preferences checkboxes.
And, of course:
Firefox does not look or behave like a MacOS program. This is intentional. It has gotten better in recent years, but it still feels like a cross-platform open-source program, which it is. But I don’t want your Linux in my Mac. I want my Mac to behave like a Mac. That’s why I bought a Mac.