You're completely (and I think intentionally) missing that flash enabled people to easily create those things... and that creativity and ease of use still hasn't been replicated (your example of Unity - doesn't come close to the ease)

People loved flash for what flash was good for (creative toys) they disliked flash when certain sites started making it the core of the navigation etc.

When people are nostalgic for flash it's for finding random toys from other people who weren't "IT people".