I feel like there's no market for this. Or at the very least, it's an incredibly niche market. Hear me out :)
Firstly, this is a pretty expensive approach to cooking, so you're already in a narrow space (people with money). There are a lot of products in this space already, from restaurants to (high quality) frozen meals etc.
(Aside - meals for 4 implies kids, and people with kids tend to have financial boundaries.)
Second you want health food. So again, more niche inside your niche. My instinct (since I've done no actual market research) is that people who are into health food aren't great candidates for subscriptions. They're into provenance, minimizing waste, and so on.
Thirdly, you're asking people to cook the meal. (Which I applaud, cooking meals is a good thing.) But cooking is easy. Once you've learned 10 dishes it's easy to learn another one. And you tweak to suit your taste. At which point your "service" is little more than grocery delivery.
Prepping food actually takes minimal time (in the real world). To a novice getting an onion peeled or chopped might be a time saver, but in reality it takes seconds to do it manually. Honestly the time spent ordering etc would dwarf savings here.
Lastly, there's little incentive for people to remain on this service long-term. Maybe it's useful in the learning phase. But it's a quick cut as skills develop. So short term, high turnover customer base.
Obviously it could be done. In a rich neighborhood you might even get enough customers to keep a delivery guy busy. But outside of SF I don't see it catching on.
But don't worry about what I think, I've been wrong many times. All I suggest is lots of market research first (perhaps outside California. )