The problem I have with these "demos" is that for all this show brought out by them, there really isn't anything brought out. The engine is doing all the work (which is expected, but at what cost?), but there's nothing that separates them from anything else. They all are practically the same in demonstration, and that's just boring.
Just today, I saw a video of a person who made a Shantae demonstration. Modeled and animated her, and recreated the environment around her lighthouse (?). Took the person 3 weeks to do that, and that's respectable, but it was the same song and dance that's been done time and time again. Move around, show some animations, that sort of thing.
It just seems people are too focused on how it looks with the engine and aren't doing anything about what makes a game a game, yet proclaim that the actual devs should make a game like that, when they aren't even providing game-like attributes that make it interesting. Moving and jumping around in a collidable environment is all basic handling of the engine.