Prioritizing or deferring to existing contributors happens in pretty much every human endeavor.

As you point out this of course predates the age of LLM, in many ways it's basic human tribal behavior.

This does have its own set of costs and limitations however. Judgement is hard to measure. Humans create sorting bonds that may optimize for prestige or personal ties over strict qualifications or ability. The tribe is useful, but it can also be ugly. Perhaps in a not too distant future, in some domains or projects these sorts of instincts will be rendered obsolete by projects willing to accept any contribution that satisfies enough constraints, thereby trading human judgement for the desired mix of velocity and safety. Perhaps as the agents themselves improve this tension becomes less an act of external constraint but an internal guide. And what would this be, if not a simulation of judgement itself?

You could also do it in stages, ie have a delegated agent promote people to some purgatory where there is at least some hope of human intervention to attain the same rights and privileges as pre-existing contributors, that is if said agent deems your attempt worthy enough. Or maybe to fight spam an earnest contributor will have to fork over some digital currency, to essentially pay the cost of requesting admission.

All of these scenarios are rather familiar in terms of the history of human social arrangements.

That is just to say, there is no destruction of the social contract here. Only another incremental evolution.