I get a lot of value from Facebook, and it greatly improves my life, even just this past week. I found out about some career opportunities through friends' posts. I saw photos of old friends that made me happy. I got answers to questions I had about a specific uncommon musical instrument I had via a Facebook group. I searched for people who would be in a city I was visiting, to message them to meet up while I was there. I learned news about acquaintences having kids or moving between cities. I read some backstory about a city hall decision that made me more informed about what particular politicians have been focused on and why. I bet I'm in the majority actually, and people who get nothing from it are probably already not using it.
Literally none of those things depend on facebook though. Mastodon, reddit, IRC, or just sitting in your aunt's kitchen for an afternoon could substitute nicely. They have no niche.
You forget about the network effect. None of our friends are on IRC. Reddit is great for some niche groups, but there are tons of facebook groups specific to a niche that really have no equivalent anywhere else.
The value being in the network means the value is subject to social whims. That's not a secure place to do business long term. All other places I listed have networks as well. You have chosen to think this network is better for you, but if/when people move then you might need to re-evaluate that as well.
No one is claiming that it is the best place forever and ever and that can never change.
But today, facebook rules from network effects. Someday it won't (just like myspace doesn't anymore).
Seconding asciident' comment here, I can count at least 3 different things that had a positive effect on me, and 0 negative ones, in the last week.
I do agree that you probably don't need this junk.