I think the issue with Linkedin is on two sides: The consumer side and the producer side.
On the consumer side, Linkedin is the worst form of social interaction one can have. It's a platform littered by unchecked success. Scrolling through Linkedin means you constantly see other people's successes.
This is not good for the human psyche. When I'm happy for a friend, it's because I know the person. They're human to me. I've seen them struggle and work hard. Success coming from them makes me genuinely happy because I know who they really are. On Linkedin, most of the posts are from people you generally don't know. Maybe an acquaintance, or a friend of a friend. They will only put up their successes. Jobs, conferences, hackathons, projects, all for social clout. Your perception of this person is crafted entirely by them, you are not able to humanize them.
This leads a jungle-like hierarchy, where getting an internship/job at a top company is the ultimate goal. Maybe it's securing funding from Y combinator, whatever it is, the Linkedin game demands this is who you become. You can only win when you do a 'top' thing that puts you above your peers. And it puts a tremendous amount of social pressure on the average person. We have a tendency to look up- even if the average person is doing worse then you, Linkedin gives you the perception that you're falling behind.
This leaves us isolated and lonely. You're not enough because everyone else is doing better than you. If there was anything you were personally proud of, that feeling is now crushed because someone else posted about doing something better than you. The more you consume, the more your identity gets stripped away. Your perception of people is now dissolved into a pile of career wins, and your pile seems to always be less interesting .
(un)Luckily for us, Linkedin offers users a chance to solidify some form of identity we've lost. This is where the producer side of things come in.
After making us lonely and envious, Linkedin offers a temporary relief in posting about yourself. You can become the producer. You feel like you're not enough? Make a post! It will make you feel better, you should be proud of your achievements, so proud that you should share it. Afterall, that's what everyone else does.
You can now create a narrative about yourself, manage your own identity. This is who you are. From your countless time spent consuming, there's now a internal social gap to fill and this is how you'll do it.
This producer-consumer cycle is present in all modern social media, but only on Linkedin do we say it's important to participate in. Under the guise of it being for your career, you are now sucked into a cycle where you are both the consumer and producer of dread. You were lured in under the promise of employment opportunities, but all you're left with is a constant need for online validation.
Linkedin disguises this cycle under the idea of motivation, but what it really is, is desperation. You become desperate to show off, you need to fill this gap. You'll always have something to prove and as a result you'll never truly be satisfied with what you've achieved.