StackExchange is pretty friendly to beginners in my experience. I used to post straight-forward questions on math and stats on math SE and stats SE. I got answers within hours and sometimes minutes, and the answers were spot on.

Agreed for the math one. I went there when I was dealing with game engines and needed something geometry related or the like rather than to stackoverflow and they were far nicer.

Even inside SO each language and topic would have different standards. A C question would not be answered in the same way one about a JS framework would.

I'm curious about the other Stack Exchange sites. Have they seen the same decline as Stack Overflow?

Stack Overflow was the "flagship" product of the Stack Exchange company, and if the company pivots to AI, I wonder what the future holds for the other Q&A sites on the SE network.

Fair point! I suspect the toxicity/usefulness has a linear relationship with how well trod the particular community is.

Ime, math.SE had a much friendlier vibe than most other SE sites. Primarily because you could ask about a problem you were struggling with and get help. No moderator would instantly show up and close the question as a dupe of a ten-year-old question about double integration techniques or some such.

People asking questions mostly wanted help, but most moderators thought they were curating some kind of question-answer form encyclopaedia. Very different perspectives.

I think it probably depends on what communities you frequent. I am not familiar with the culture at stats.SE, but math.SE has a (semi-?) explicit mission of being more friendly to beginners than MO. I think that many communities aren't so friendly, and don't have beginner-friendly analogues.