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".
I’m not being intentionally obtuse. I’m just not viewing a dead technology with rose colored glasses.
If you don’t like unity on account of being too powerful pick from the dozen or more easily found projects that do what flash did in the same creator friendly way. Here’s one: https://www.wickeditor.com/
Again, people didn’t love flash. They loved the content that was created. Having to deal with updating flash and all that hassle was something people tolerated to see funny animations that anyone can still make today. The concept was very cool, the execution was not.
Everything flash could do from a creative standpoint is easier and better now, with the added benefit of not being awful ux.
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".