In the long run, I honestly think kitchen-only setups optimized for efficiency & food safety will grab a big share of the market. They can experiment with vertical integration, and avoid all the hassles & limitations of sit-down dining. They will be able to more, better, faster and cheaper. It might be hard to copy & paste the entire thing from one city to another, but the core functions should be quite portable.
It would be crazy smart for someone to standardize an interface (e.g. REST API), let restaurants implement glue to their systems, and then allow a plurality of delivery services to consume and order through the standard interface.
It needs to be a protocol like email or http, not another company with a proprietary aggregator.
For delivery it's harder because you actually need someone to deliver the food and the logistics are really hard (they have to get there when the food is ready but not too late and not too early, etc.). But... there are like 80 restaurants in a 10 minute walk radius from me, so I can just deal with pickup for now.
The best part is actually just having a variety to order from. Before these delivery services, there were only a couple of pizza places and a couple of Chinese restaurants and nothing else delivered.
For a lot of restaurants, it never made business sense to deliver, and still wouldn't. But when the delivery service is spread out over many restaurants, it works rather well. That's good for both the businesses and the customers, despite the friction added by the middlemen. It's a real win for people who couldn't as easily go out to eat, due to health or disability or whatever, but also for everyone else.
Visa, Amazon, Apple, Google, or Paypal sort of provide that function, but being able to shop many restaurants with a single identity has its benefits. Something that wouldnt be fixed just by restaurants with nice websites.