So to some extent I wonder how possible it is to just...  order pre-made assets to slap together into a game.

I know that every game engine basically does this already, they come pre-packaged with a ton of built in assets that you can use, but I'm starting to wonder if there isn't just bigger, and bigger, expansions to these.
Like if there isn't totally just a way to keep ordering pre-made asset packs, and keep tacking them on, and occasionally higher an artist and a code monkey to slightly edit the masks, and tweet the AI a bit...