I think some of the actual value of delivery apps has been that they have low start-up costs for restaurants. They aggregate demand for that channel and some of the genius here is that it's pretty simple putting a restaurant's menu online.
It seems clear to me that there is plenty of demand to justify the service. Doordash's revenue was about $5B last year (I believe that's revenue and not GTV, which is probably 5x that). Doordash also only has about 50% of the market. Even if you believe that some of that demand is illusory, brought about by subsidized prices, that still seems like there's a pretty straightforward business there if you can charge a sort of "ordinary business profit."
And, again, there's been delivery food businesses since time immemorial, it would be weird if we thought that there was no kind of business here. Pizza companies used to be more or less the only ones because pizza delivered so well that pizza restaurants could absorb the fixed cost of entire delivery employees, but a food delivery app lets you pay for just part of a delivery-person.
It seems pretty straightforwardly the case to me that the problem in food delivery apps has never been that the fundamental business makes sense, the problem has been that from the very beginning there have been a large number of companies ferociously competing in the space, with nothing to differentiate them, which has squeezed margins to nothing.