How LinkedIn failed:

"Over the last year, contempt for LinkedIn became a bona fide cultural phenomenon. The company’s signature catchphrase — "Hi, I’d like to add you to my professional network on LinkedIn" — was posited, plausibly, as the perfect universal entry for The New Yorker’s long-running cartoon caption contest. LinkedIn also admitted that hackers had made off with 100 million email and (hashed) password combinations from its servers, which led to a number of high-profile Twitter accounts being compromised.

Meanwhile the company’s aggressive email tactics, which needlessly opted users in to receiving multiple messages every day, resulted in a $13 million settlement last year......"

"........LinkedIn held true to its vision, built a very smart team, and used a dizzying array of growth hacks until it became ubiquitous. Today it has 433 million registered members, a quarter of whom visit it each month......."

".........It loomed large but has never been essential, focusing on its paying customers at the expense of the users who make it valuable in the first place. The company makes grandiose claims about creating economic opportunity — CEO Jeff Weiner said this week that LinkedIn will be the answer for workers who lose their jobs to robots. But in practice it’s not much more than a way for white-collar workers to field occasional inquiries from recruiters and vendors who pay dearly for the privilege. Or, viewed from an acquirer’s perspective, a rich trove of data that would be better put to other uses........"

Overloaded and flooded by those who are not worth employing and/or who are destroying/underbidding the value and quality of all services offered on the free market.

https://www.theverge.com/2016/6/14/11933166/linkedin-microsoft-acquisition-thirsty-email-company

So there you have it, a little more to it, but essentially you have hit the nail on the head.

I shall not mention other sites as they too are failing drastically, as the vision set has been forgotten and the greed factor has taken over. "Anything for a quick buck".