But I would argue that it usefulness only extends to its body of knowledge. As a service and/or community it has been pretty terrible for a long time:
If you were a new user trying to learn programming, it was maybe one of the most toxic resources available. I don't think I have posted a question since 2019. And even there, the only thing the average user could expect was a snippy response from someone who barely stopped to read your post. And/or a mod deletion because a similar-ish question already existed (regardless of whether it had a satisfying answer).
At a certain point, all the meaningful questions have already been asked. The site exists to collect novel new problems and not help people with iterations on existing problems.
(Also, underrated is the extent that the industry has homogenized around a couple of frameworks that are used for everything. I think it's telling that the peak of StackOverflow coincided with the era that React was taking off, to just name one).