I don’t think there’s a hard obvious line, but if I invent a machine that can take $1 from every other American’s wallet and put it into mine I am quite comfortable calling that “untrue” innovation.
When thousands of companies have opaque versions of this business model, you notice it on a macro level
When DoorDash puts themselves as a delivery service front end for restaurants without them knowing, and then raises the prices, that is simply legally stealing money. The restaurant, on the other hand, actually sells something of value.
There's more nuance to these issues that you suggest. The U.S. government is investing in tech for various legitimate strategic reasons you can read about. Government bureaucracies historically fail to produce (or contract) good products for reasons you can observe by working at one (or by reading Dilbert). Many tertiary sector businesses are indeed just middlemen but still create value in a more complex way.
I get it that tech can be criticized in the way you're doing it. This discussion had been had thousands of times on this site. I have nothing to contribute besides what I already said, and even all of that had probably been said thousands of times as well.
How much would you pay for a machine that steals a dollar out of everyone else in the world’s pocket? Maybe you’re a good person and the answer is not much but I’d guess most people would pay, say, 7 billion for it.
If you’re asking about DoorDash specifically, people pay because they think that’s the price. It still damages the restaurant’s reputation, lowers their order numbers, etc. it’s legal stealing.