The economics are different - though I'd hesitate to call them
very different, but that's probably splitting hairs.
I just took a look at the Munchery menu for my zip code, and honestly not sure why I'd ever use them in a market as competitive as NYC. The "aren't locked into a specific menu style" thing seems like more of a bug than a feature - lack of specialization means I drift towards more specialized restaurants that deliver.
Why go for their beef stroganoff when I can get it from the amazing Ukrainian place that delivers to me? Why get the Korean rice bowl when there are several Korean places nearby? Chicken teriyaki - no shortage of Japanese-focused places that deliver, also.
The nature of NYC's food market (and I'm sure true of other places too) is that delivery restaurants are running incredibly lean operations on razor thin margins - I think it's far from a given that a no-front-of-house-delivery-only restaurant operation can generate the kind of numbers that justify stratospheric VC-tech valuations.
I'm also skeptical that they can achieve the kind of volume/market share they'd need to make their unit economics work. There seems to be this weird idea that, by serving 10-15 dishes a day, that they can capture a significant fraction of the total delivery orders in their service areas - in every zip code they operate in NYC they are up against literally hundreds of other delivery places.
To the consumer they appear as one restaurant in a sea of many choices - I don't see how they can expect to capture and outsized portion of orders this way.