If by "even though all they've really done", you mean,
(1) They've opened several proprietary warehouses,
(2) They've developed direct sourcing relationships with numerous farms, cutting out any distributors/wholesalers/etc,
(3) They've hired chefs to figure out how to take real-time supply data from (2) and convert it into recipes, with the right portions, that account for seasonality, weather, and other supply variations,
(4) They've executed a consumer marketing campaign that's led to over 159 million meals served across 25 million orders
then sure yeah, they're just a "costly middleman".
I don't use this service, but you might try reading their S-1. It contains a lot of interesting commentary on their strategy, and hard data on the business. I don't know whether this thing will be worth its IPO price, or have a lot of upside when it goes public, but I do think there's space in the market for a company that handles all the logistics and gets the exact right quantity of stuff on your table. Per their S-1, 21% of all food purchased in the US is thrown out - that's plenty of room for innovation.
Also, consider that they've done all this on $195 million vs. $675 million blown by Instacart. I know for sure which one I'm more impressed by, but you be the judge.