I'm not sure what you mean by this. Roblox is literally a game engine, the entire point is for people to create mini games and share them. That's basically all that Roblox is, if you go to the homepage it's just a list of games you can join.

And you can validly complain about the technical quality of tools like Scratch, but as much I personally hate to admit it, Scratch is more user friendly than Flash was. I personally know kids who are making stuff in Scratch that would not be able to handle Flash. It's extremely crude stuff, Scratch is ridiculously limited. But they're still making stuff and sharing it, and getting their friends involved in the process, and sharing hacks with each other to get around its limitations, and finding other projects that impress them and reading their source code.

I do get what you mean about Flash's technical side that made it interesting. I miss an animation-first workflow, I wish someone else would build a tool that experimented with that. There is definitely a hole in my game-dev process that Flash left behind. But in theory, you could still be using Animate today and exporting your games to HTML5. Nobody has explained to me what's broken about it.

But if everyone in the old Newgrounds scene moved to Animate, or if it was magically released for free tomorrow, would that bring back the community? I'm not sure it's that simple.

I don't think that kids stopped being creative when Flash went away. I think that people (myself included) who grew up on Flash got older, and the spaces are different now and we're not being invited to them. Which... I don't know if that's really a technological thing, or even necessarily a problem that needs to be solved. Were there really a ton of 35-40 year olds making stuff on Newgrounds back in the day? I am increasingly learning about community spaces from the kids I know that I would never stumble on by myself on the Internet. And they seem to be pretty vibrant, they're just not my spaces anymore.