>> If restaurants put any effort at all into fixing those things, there would not be such a strong demand for apps.
In such a world, Some model of Ghost kitchens will thrive anyway, not small restaurants.
Why ?
The area a kitchen serves will become much larger - distance matters less when you don't need to go pick the food. And even when food freshness matters, there are some solutions like parcooking and finishing the cooking in ovens inside delivery vans.
The type of food a kitchen serves becomes much more varied - today your Chinese restaurant has one kitchen, and the Mexican place has a different one. But with delivery-only, a single kitchen can open many virtual restaurants.
This also helps with delivery - a single family who likes different food, can order from the same kitchen, and get the order delivered in one go.
And this is now an internet business - since customers prefer all the restaurants in a single app, single search - and those add new complexities.
And usually, small business(in aggregate) often had the benefit of agility over large businesses. But a virtual restaurant is very agile, conducting business experiments is rather cheap.
And personal service and deep relationships don't exist in food delivery - and that was a weakness for big businesses over small ones.
So long term i don't think delivery a good place for restaurants to be.