Fresh is cheaper, more accurate stock, doesn’t require interacting with the shopper, has more available delivery times, more vertically integrated, and (subjectively) a less crappy website - easier to do basic things like add old stuff to order without it doubling numbers of things already in cart. Instacart website was also noticeably slow.
This isn’t personal - I just wouldn’t invest in or use instacart again given the alternatives. I think my anecdote is relevant since you work there, customer experience sucked.
I wouldn’t bet against Amazon in this case. A middleman service will always lose out to people who own the full stack.