From what I’ve observed, people are increasingly checking out of social media (or turning their profiles private), because it’s just unappealing unless you’re actively promoting something.
This is social media unless you change your nick often, but even then people run stylometric analysis all over this site. Nobody is truly anonymous on the internet.
The numbers just don't support this, though? Social media remains at an all time high in engagement numbers. And climbing.
What is also growing is the number of people signaling that they are out of it.
This is extra pernicious because the people that are staying in control of these environments are maintaining a large amount of leverage over everyone.
The phenomenon I'm describing is people switching to consumption-only mode, or only posting privately. I think you're right that engagement is going up, as people treat social media more like TV and less like microblogging. I define that as "checking out."
It's just a huge change from the early days of social media (Instagram 1.0, Flickr, Twitter, o.g. Facebook), where nearly everybody who was active on the platform was also posting.
Note that that survey asks what social media U.S. adults ever use. Time on site, trending over years, would be more interesting to see, but I'm having trouble finding any recent research.
I have seen indications that Twitter is actively shedding both readers and time-on-site, and that Facebook/Meta numbers are strongly buoyed by purchases (WhatsApp, Instagram). Others I'm not so familiar with.