Maybe not 'fixing' a problem, but they certainly vastly improved on the existing service aspect of food delivery. Which is the aspect I care about.

Buy from places that have their own delivery service

Figuring out which local restaurant does and doesn't currently deliver (which would change on a daily basis) was one of the main problems. Restaurant can still have their own delivery drivers but having a central place to look up who is currently (in-real time) delivering and what is a big improvement. Also I don't want to call or talk to people, so every restaurant would need it's own system to take online orders. Doesn't seem realistic.

Actually walk or drive or public transport to the restaurant and eat out

Brilliant. You can also cut down on commute/travel time and cost by just staying home. Or fix your depression by stop being sad! Big brain.