It seems to be good in theory, but I'm not really buying into any of the implementations of ECS, CGS or whatnot until they have a working, non-trivial example.

It seems to be good in theory, but I'm not really buying into any of the implementations of ECS, CGS or whatnot until they have a working, non-trivial example. If they have really thought it far enough, then they should have at least have a complex game as a solution to a general problem they are addressing. The demo in that repo you linked can be trivially implemented, CGS or no. Someone could rebut with: it's only a demonstration, but it's easy to scale any game of any size. In theory yes, but theory and practice aren't always friends. The actual complex game could serve as a proof, and the author can enumerate the pain points and limitations of the framework. Wouldn't that take too long? Not really, just copy an actual released game, but using shitty (I mean, free) assets and make up some random content. It should cut the total development time from a week to a month at most. By copying, I mean everything, from the main menu, to in game-menu, to the little bits of logic that makes a game fun and engaging.