I’m not all that familiar with food delivery as a business but IMO from the perspective of a customer, the reason these companies are closing down is pretty simple: they’re not building something people actually want. The benefit of a few extra places to choose from when ordering takeout is minimal at best; the choice on Deliveroo / Uber Eats is not exactly small, and the incremental gain from a service like Jinn’s is unlikely to ever gain a large loyal following – the barriers to switching / using other services are ridiculously low.
I would argue that a precursor to becoming a massively successful startup is that users become somewhat dependent on the product/service. I.e there’s a genuine reason it’s 10x better than any other option and it solves a burning need. That simply isn’t the case with food delivery.