I think you are misunderstanding his rationale and message. The message, the way I read it, isn't just that you don't know the random project, but you don't re

I think you are misunderstanding his rationale and message. The message, the way I read it, isn't just that you don't know the random project, but you don't really care about it. He says to not just bring a brick, but to build a great school. The AUR example is relevant, because it is a problem you (he) cares about and continues to nurture, not just add a brick/PR and leave. It's not gatekeepy because it doesn't say "don't contribute". It says "contribute to something you care about and want to succeed, where you will put in more effort than just a one-off, for the sake of the project and not for the sake of learning". Most projects can find use for a junior developer contributing consistently if the dev will learn the project and domain. It's not gatekeeping.