This is rarely a problem with Ocado, which I use. Their stock management is good - they're not picking up from stores but from their own increasingly automated warehouses. Very occasionally they do run out, in which case they ship you substitutes. If you don't want the substitutes they take it back to questions asked, but it means it's rare I get a delivery where stuff is missing and there isn't a viable replacement.

Ocado is increasingly licensing their warehousing platform internationally, so it's likely to show up near you.

I'd agree with you if we were talking about staff picking from a shop floor - that does not work reliably enough at all, but that model is several years outdated and the only reason some of those still survive is that the more automated systems like Ocado's and a few others are a lot more capital intensive to roll out as it means building dedicated specialized warehouses.