I was thinking on the same lines but we have Mastodon and Fediverse today that still need to grow beyond the techies of the world and include business folks or even recruiters. A supply and demand use case.
Recruiters won't use a thousand instances, they will use one main instance, where users can be unilaterally banned without explanation just like on Linkedin. The problem is not technological, and can't be solved with tech. The problem is social, and must be solved socially, i.e. we need to demand better human moderation and rules.