The only thing making SO decline is that they have a CEO. And that CEO is trying to "compete".
Just keep being a great platform for Q&A and stop chasing profits. People prefer SO because the ansewrds are trustworthy. LLMs will always bullshit you and never be better than a platform free of AI crap.
The decline has accelerated since the release of ChatGPT, which suggests there may be a connection, especially given ChatGPT's ability to answer many coding questions.
I agree. That being said, there is some majorly bad answers on stack overflow. 9 times out of 10 I get wrong answers, and one time I was looking for a solution in Arduino and someone answered in Javascript for some reason.