Facebook being used as a way to keep up with friends has been fading for a while. It's mostly only older people left on it, Elder Millennial and older (I'm an Elder Millennial fwiw).

Facebook's real social media power is in its groups and pages. There's usually local town groups, like you'd have with NextDoor. But there's also giant meme groups. New Urbanist Memes for Transit Oriented Teens (NUMTOTs) is huge, and is basically posts about trains and hating landlords, but it was big enough to the notable when the group endorsed Bernie Sanders in 2016. Another huge one is Wild Green Memes for Ecological Fiends, which is memes about nature and wild animals. Facebook has become a lot like reddit, in that it's what you make of it in terms of weird friends and niche groups.

The current go to joke about facebook goes like this:
"Facebook is lame, there's no one on it anymore and it's no fun."
"Facebook is still fun if all your friends are gay communists."

FB is mostly used by the 40+ crowd.

IG is mostly 25-40

Tiktok is predominately under 25.

I use Facebook to talk to about a dozen or so people I wouldn't otherwise. I know, because I dropped off for a couple years and didn't really connect with them, which sucked.

But on a day to day basis? It's the absolute worst dregs of boomer humor and low effort, brick stupid content. It took a long time to screen out the political garbage I hate and slowly unfollow the various people who've gone insane in the past 8 years. I was left with like ... purposefully bad cooking videos, advertisements, the occasional comic book page (why?!?), more advertisements, old/bad memes, more advertisements, and most important of all, advertisements.

In fairness my wife uses it to coordinate with other parents from our kids school. Why we can't use something else to do that coordination I don't know, but eh.

tldr: It's for older millenials on up and mostly garbage algo promoted content thoroughly seasoned with advertising.