Q: Why is every social media site dying?
A: i could sum it up in 3 words: Greed, anger/hate, ignorance.
From a information sharing perspective, social media sites are often just echo chambers for quackery, sharing rubbish or each user just putting another shade of lipstck on the same pig.
And its the big data concept that also has ruined the party for everyone, its the reason you see so much intrusive advertising etc, because your scribbles and data was "mined" by the site like bitcoin and traded.
Then of course one has to mention AI that is f*cking it up everyone on the datesites, nothing but greed has lead those sites to employ bots to give attention to user profiles in order to entice the user to pay for a subscription and make sales