I won't call it dead, but it is declining. Their various sources of traffic are now regurgitating Wikipedia Content (and other 3rd party sources) via uncited/unlinked AI "blurbs"...instead of presenting snippets of Wikipedia contents with links to Wikipedia to read more.
It's not the only reason their traffic is declining, but it seems like a big one.
I may be wrong, but I don’t think the people that edit Wikipedia are the same people that are content with half truths from LLMs and thus no longer visiting the site. So I kinda doubt it matters much.
Also, Stack Overflow is a commercial website, while Wikipedia is a free (as in freedom) project. Editing Wikipedia feels like you're contributing towards "an ideal", that you're giving back something to humanity, instead of just helping somebody else getting richer.