The kind of PRs I'm talking about are from people who have never and likely never will use the software, but want the badge of questionable honor of having contributed to a well-known project. The only reason they looked at the code is because they saw it in the news or someone told them to "go contribute to open source" to help their career. I don't mind a junior going to fix a but that they themselves found and know how they want the software to work. I do mind if someone goes randomly looking for something to contribute without understanding the software, how it's supposed to be used, and proceeds to expect maintainers to hand-hold them through the process of getting their contribution in so they can put it on their CV or satisfy a teachers assignment.
I think what's rarely spoken about is the fact that each PR needs maintainer time. Maintainers are typically few and their time should be used to further the project, not for personal gain.