My experience with Stack overflow from early 2010s to now, is that it used to be an amazing, "must-have" site. Always the #1 result on Google. I used it for basic web and iOS dev (remember Objective-C) and it had better documentation than most of the official docs.
But now the quality of the questions and answers is worse, official docs are usually much better (at least in my experience), and there are a lot more random sites, so you can Google most programming issues without checking SO. SO is still a great resource for its archived content, but not for anything new, and it's no longer a "must-have".
But even with better documentation and more sites, old SO hasn't been completely replaced.