I think you overestimate 2 by a longshot most problems only appear novel because they couched in a special field, framework or terminology, otherwise it would be years of incremental work. Some are, they are more appropriately put in a recreational journal or BB.

The reason the "experts" hung around SO was to smooth over the little things. This create a somewhat virtuous cycle, but required too much moderation and as other have pointed out, ultimately unsustainable even before the release of LLMs.