I don't like that they inflate prices and will not order directly from them because of it. They should be transparent about how much their service costs rather than hiding the true cost of their service in the item prices. I feel like it's likely their fault and not the restaurants since it seems like every restaurant has inflated doordash prices. My only theory is that they may be charging the business service fees in addition to the service/delivery fees they charge the customer.
They do white label delivery for a fast food restaurant I order from. I've had it take 2 hours to deliver multiple times and even had one order get cancelled by doordash after they couldn't get anyone to pick up the order. Most of that delivery time is made up of it switching between multiple people who they expect to pick up my order. Once someone actually picks up my order it only takes about 5 minutes to get to me.
Also in my experience (in Chicago) the food in the app costed $1-2 more per item (this wasn't listed anywhere, but if you compare the cost with what the resturant charged it was a lot more).
Also there was at least one resturant that I visited that would give you less if you ordered through a delivery app to make up for the fact that they had to pay a fee. This is shady and shitty on the resturant's part and not really DD's fault (although frankly it's kind of predictable) but it was still a thing that happened when I used the app.
I haven't used it for about a year though (because of the above shady practices) so they might have changed.