I've had enough reputation to see the moderation queue for years now. Imo, the site is anything but welcoming, as it shuts down newbie questions all the time with zero guidance.

In spite of this it seems like most of the activity is for what I'd consider very low-value questions.

Already when I was a student working on my thesis, my issues were too advanced to ask questions on SO. I asked but I got no replies.

At the time I would answer to others. Now I don't really bother. I often see a wrong answer being marked as correct, because it came before an actually good answer.

For me SO now is at most a website where to copy boilerplate stuff like "how to create a unix server socket".

Welcoming and newbie-friendly are not the same thing.

QFT. There should be mandatory 'why this question was closed' in cases there was and (misinformed) effort. Currently it's -10 closed, no comments.

There is?

Nothing is worse than asking a question. And it gets closed as duplicate. You click on the duplicate and it’s asking a different question or obviously not the same thing. And they refuse to reopen the question.