Have you seen the backlash in gaming circles about game studios that use AI? Lots of gamers will avoid your game like the plague if there's even a hint of AI generated 'artwork' in it.

There are lots of open source games or game engines where the artwork is trivial to acquire and lots of people enjoy them. But these engines also have to be maintained to be available 'forever'. The business model of game development seems not really suited to open source, lots of games are ripped off within days and posted on app stores with a slightly different name. And that's with proprietary code, with OSS it will take even less time. If you can't sell it you can't live from it and if you can't live from it you don't have the time and incentive to make a great game.