Here in the UK, every big supermarket does online delivery, and it's popular - all the ones I have used have the same process - they tell their pickers to pick

Here in the UK, every big supermarket does online delivery, and it's popular - all the ones I have used have the same process - they tell their pickers to pick like they were buying for themselves (try to get long dates, try to pick good fruit/veg), allow you to ask for specific things (less/more ripe, bigger/smaller), allow you to reject anything for any reason at the door, replace items they don't have for alternatives (including bigger sizes/premium alternatives) without charging you more, and tell you about anything on the order sheet (this item is replaced, this item is short dated, etc...) and put them into marked 'check this before accepting' bags. I was intially sceptical like you, but I've found the quality is the same as if I'd picked it out myself. Obviously, there is no guarentee that is how another company would do it, but it does seem to be accepted here as the norm.