> I'm using polling requests instead of websockets because I'm lazy/it doesn't need to scale, but it's the exact same idea where the server just publishes a giant JSON object of state and the clients are pure functions of it (and send messages to the server to mutate it).

I like this approach as well, but I do worry that users today expect optimistic updates on the client, and the injection of a X00ms delay would make the app feel sluggish.