It seems like its mostly old people on Facebook now, at least that's my perception as a millennial who interacts with mostly other millennials
This isn't even mentioning the rampant misinformation and divisive bullshit permeating the platforms (yes both of them)
The more socially competent you are, the less useful this probably is. Many people probably have some useful network of friends they built in college. I have little to draw on aside from a handful of people I worked with which I had professional rapport with which I never developed a personal connection. So thus, I am stuck on LinkedIn on the off chance I need a new job and a reference.
People also have large group chats, which is a trend across all networks and general interaction.
Easy to miss that this trend is happening if you aren't part of any.
Its publicly accessible content on social networks like this which are going by the way side. The engagement is much less visible.