The problem looks pretty clear to me.
Facebook and Instagram both got popular as social media. Interacting with your friends.
However ads stick out like a sore thumb among updates from your friends and your friends don't create enough interesting content to keep you doom-scrolling all day to view more ads. So both transitioned to public entertainment (still called social media for legacy reasons, there is little social about this side of the platforms, it is just media consumption). However this doesn't seem to be as popular (young people want to talk to each other and show off to their friends) and other platforms that don't mascarade as a platform for friends are doing better TikTok and YouTube.
It seems like Zuck needs to either
- Figure out how to monetize actual friend-to-friend interaction.
- Build a platform that is designed for public entertainment, not pretending to be for friends.