I think overall we are agreeing. USENET and various sites were a huge jump from the state of things before hand, when your available resources really depended on location. SO is a more useful interface on top of that stuff and easier to access, but the real innovation was made decades earlier.
The next version might implement a versioning strategy, say questions/answers get archived every five years or so.
Before that, you'd get books out of the library and get a pad of paper and hand-assemble 6502 code and read Byte magazine and if it took a long time, you learned it very very solidly. So I'd say I got a level of deep understanding from hand-assembling code for 6502 that I (as a fogey) doubt I would ever get from any amount of SO reading. Tho my general work flow once I start typing is to google every thing that I can't instantly fix; weird compiler error, cut and paste into search bar, optionally add "stack" to the end and read.
Agreed. I remember using https://www.codeproject.com/ a lot, back in the day. The quality was often variable, but being able to search for function-names and see them in use was very useful.
Especially when the only alternative was years-old MFC books in the local library.
Therefore, at no point in time have I been dependent on google, though it was helpful about five to ten years ago. So, my impression is that SO was the bigger innovation, though YMMV of course.