Until the contributions are cheap and correct, you need valuable contributors more than you need the contributions.
You point would be valid when we get to a point of contributions all being both correct and cheap. Right now they are only cheap.
It takes like 5 minutes to spot garbage PRs manually. LLM can flood you with a wall of text where only half of the stuff make sense. Also, they can't really spot bad architecture. It's a compiler in an unpopular language, don't forget that.
The real bottle neck when you want to grow is connecting with the right people. An LLM is not helping with that if you want to build a community. When you use LLM to skip the need to understand a problem how are you ever going to get a reputation that I can trust?
The post is not about reputation it about seeing how people respond and work with you in a community.
EDIT: I see that you frame it as a help and a tool and sure it might work, but I feel like it is just another obstacle.
I suggest we also automate the distribution and the use of software with AI as well, and then just all go to the beach and sip on some cocktails or something.
Or in other words: Good luck with that.