That may be part of why they aren't doing well.

Once you know how to cook, you don't really need the training wheels any more, and the cost of their overhead is just that: extra cost.

I have a hard time imagining them beating grocery stores / delivery long-term.

Maybe if they get enough customers to get economies of scale so large they can offer meals cheaper than grocery stores, despite their extra overhead (meal planning, recipe development, and software maintenance come to mind immediately).

I could tell this "mail order meal kit" industry was doomed when local groceries tried to hop on to the trend (selling the boxes in their stores, with very little overhead: no need to ship an insulated box across the country), and it didn't take off.

Well, if you're already at the grocery store, you probably have a shopping list and a pre-filled box isn't what you're there for.