I was going to post a comment about Instacart here, but instead decided to write a little thing on Medium. Why Instacart is gonna get crushed by Amazon https://medium.com/@a13n/why-instacart-is-gonna-get-crushed-...
You select your local supermarket, and it has a pretty good idea of what they actually have because it's an official service. You can also specify per item whether substitutions can be made, and if necessary they'll try to find a good alternative (like your "different salsa") if they can. The times you end up with a substitution or no item sound VERY low compared to your experience with Instacart. You might order 40 items and get a couple of subs if you're unlucky.
It also sounds cheaper than Instacart. It costs around $10USD for delivery (depends on how much your order), or around $3.50USD if you want to collect from the store,which is still super convenient because you just go in and wheel out your already-full trolly.
I'm kind of surprised that supermarkets doing delivery doesn't seem to be a big thing in the US. Usually we're the ones who are a few years behind.