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.