The vast majority of AI-driven contributions are worse than useless. They contribute nothing of value, and cost a lot of volunteer-time to filter out. Not having an endless deluge of AI-driven slop contributions is a net positive, as it prevents the existing contributors from burning out.

Sure, it might hurt some vibecoder feelings that "Claude, write a useful contribution to this project, make no mistakes" returns in them getting banned rather than a mention as a valuable new contributor of a load-bearing OSS component, but that's a price many projects are happy to pay. Any genuinely valuable new contributor would have no trouble spending five minutes writing a PR in their own voice, before asking volunteers to spend fifty minutes reviewing it.