Like any new social network, the first question to answer is: how do you make it useful -without- the social layer?

Instagram did photo filters.

LinkedIn did digital résumés.

Strava did activity tracking.

It's not zero sum. But if you're going to replace LinkedIn, you need to ask yourself: why would someone want a -new- digital résumé?

By the way, these things already exist, albeit in a more niche capacity, which is a good thing. GitHub is LinkedIn for programmers. Behance is LinkedIn for designers. X is LinkedIn for AI scientists :). Etc.