I usually at least make a decent attempt at resolving these types of conflicts before reporting to AMEX. Even though AMEX's chargeback process is probably the best of the credit card companies I've used, it's still not as ideal as simply getting the refund from the merchant, if possible.

Oddly enough, I've NEVER had this issue with DoorDash. I think DoorDash simply makes restaurants unavailable if they don't have drivers, whereas UberEats ALWAYS takes the order and then simply doesn't fulfill it if they can't. What you say about "preparing your order" is 100% correct. There isn't a "waiting for driver" status, so if there is no driver on the way, it stays at "preparing..."

This is a particularly terrible customer experience since you almost always time your deliveries so you eat them right when they get there and you are hungry when they arrive. By the time you realize Uber is not going to bother fulfilling your order, you've already probably been waiting 30 minutes, cannot cancel then without being charged, and have to start making other plans for food as you get hangrier and hangrier. It's even worse when you're getting food for the whole family delivered and have to deal with hangry kids!