You are quite the exception. Most people don’t even have a computer and get along with an old Android phone for everything (as admittedly, it’s quite enough)
Yeah, it's unfortunately rare, but it is easy: on mobile you could install some separate browser app. In Chrome on a desktop it's two clicks to switch profiles, and about three to create a new one. I used to open an incognito window for Facebook, but you'd have to log in anew each time.
Of course I wish people would leave Facebook instead. I'm doing my part by not posting there.
