I used to think so too, but then I realized that Facebook would let people add me to group chats or something without my knowledge and that these people would then blindly assume that I had read the messages in those chat groups. I find that "I have a Facebook account but I almost never log in" tends to get misunderstood, whereas "I no longer have a Facebook account" gets the message across quite clearly.
You think that once you log in to FB in a container -- Facebook can't track you? Those container details are now appendage to your online fingerprint as far as Facebook are concerned.
Containers only work if you don't actually log in to such services. The only sure way for FB to not track you is to not use FB at all -- even then it requires other steps too as they'll be building a shadow profile on you.
Is that naive?
Facebook wants to be addictive, but it's okay and possible to use it once every two or three months so you can add your great aunt and post holiday photos (so people know you're safe). And by using Facebook less, it takes away some of Mark Zuckerberg's power over you and our society.
Edit: Oh and I use it in a Firefox Facebook container so I'm not at all worried about it tracking me online.