I haven't watched any Mazes playthroughs, but I can imagine why you had that reaction.
Like you, what appeals to me about Polymorph is that the core resolution mechanic is so very basic, yet allows for a few surprises.
My own design goal is to create something that scratches my PBTA itch while being even simpler.
One thing I've enjoyed about PBTA is that all of the character creation stuff is on the character sheet itself. While I haven't quite gone that far here--mostly because I'd need to make 12 different templates--I still like the ability to stat up a character in a couple of minutes.
Another plus of PBTA--specifically Dungeon World--is that there are no lengthy explanations of the how, what and why of monsters. They get a few keywords and some stuff they will do when someone blows a roll.
There aren't any rules for how a Medusa's petrification works; a Medusa turns someone to stone because that's what a Medusa does. And there's probably a magic spell that can change them back, but it will take research and perhaps an exotic ingredient or two.