Maybe you are not aware about technical details, but it is literally just sandbox, what you can use to any website regardless how it is named. Using Facebook as example is just marketing.

In the recent Firefox versions, they are called only as containers.

I think you are talking about what used to be called "multi account containers"? That's obviously not viable unless you are a "power user", imagine for example a non-tech-savvy person having to enter all of the domains that Google uses, there are dozens of them as you can see here https://github.com/containers-everywhere/contain-google/blob...

Or maybe Firefox containers have changed now? I haven't used FF in a couple of years, how does it work now?

Based on the READMEs, functionality is quite identical on Firefox's build-in containers.

Only difference which comes with these extensions is, that they work automatically for selected domains, instead of you manually opening the site in container. Also, you need to be careful to not open other pages on container tab, which is possible. Maybe I was thinking this to be too obvious for most users, while it is not.

But yeah, there are plenty of domains if someone is really using all of them. However, it is pretty hard to miss Google login window for example.

Of course, one could speculate that one login into your Google account from your browser is enough to fingerprint you everywhere, even with all anti-fingerprint things, but that is another story.