LinkedIn's value is that everyone is on it. Even super secretive Apple employees - Apple couldn't force them to delete their stuff. Talk about a powerful network effect. Just start browsing, see for yourself: https://www.linkedin.com/company/apple/people/
LI's value is not in the UI, not in the features. Just like FB, YT, WhatsApp, etc - they took off while no one else did, not because better tech, but by hitting a virality inflection point.
This is a hard problem to solve, people like Nikita Bier are the equivalent to rocket scientists in that area. And while they can launch a viral app for teenagers, the "easiest" early adopter group, repeatedly and flip it for cash - they can't figure out how to crack LinkedIn.
Think of it as a virus/pandemic problem. Who are the super spreaders that pull in the rest of the normies? What is the initial value for THEM to join in the first place? I can tell you that a special social network for Doctors, publicly listed now, had to give their initial cohort of docs STOCK in the company to be on the platform. Talk about dilution...
So, sorry, forget about the shiny UI. How do you infect and take over the LinkedIn host? They fight scraping left and right.
Personally I am so happy to work in enterprise SaaS...so much easier than the above :)