The thing is, bad questions don't really matter in the grand scheme of things. If a question is bad, and it gets no answers, it will just languish. You don't need to do anything about it. Maybe have an auto-close after a week of inactivity or something. It probably doesn't really matter, as long as you actually sort questions by things like score, answer score, etc, so the bad questions just go down to the ends of all of the lists on pages no one ever browses to. Bits are cheap, a few bad questions being present on the site and not closed doesn't really hurt.
I don't expect every bad question will lead to a valuable mentorship opportunity. I've certainly encountered my fair share of those that weren't worth spending my time on.
Bad answers are more problematic; there's good reason to be vigilent about those.
And of course spam, obvious homework, and just completely incomprehensible questions should be closed instantly.
What I see is questions which are not phrased well but you can actually work out what they're asking being closed. So by the time I've written up an answer, the question is closed, and my answer is wasted. I can copy my answer elsewhere, and vote to re-open, maybe after editing the question to make it more clear, and it might get re-opened, but then I have to spend a lot more time and attention waiting for that. By closing out questions too aggressively, not only are people putting off newcomers, but also wasting the time of those answering questions.
> The first post review and triage queues are intended for providing this help. You can see that this doesn't always work well ( https://stackoverflow.com/review/first-posts/19570266 or https://stackoverflow.com/review/first-posts/19569647 - note the not even trying to fix the grammar of the question or asking for the necessary information or providing help on how to improve the question, just no action needed)
Yeah, one of the things that really frustrates me about the review process is that they just incentivize taking some quick and easy action, not actually doing the right thing.
Effective moderation is not easy, and a very different skill set than answering technical questions, but the rep needed to perform many of these mod duties is just given to those who accrue enough rep.