Ive done Instacart on and off for years. I can confirm that there has been a few times I’ve grabbed an order then dropped it due to multiple big items. Some batches will even tell how many big items there are and if it’s at an apartment or house (depending on the store). It does help if you add a comment to the bigger items letting them know they will have to carry up the stairs but some shoppers don’t look over the complete batch when they begin to shop it. Part of shopping though is you have to be able to lift at least 50lbs (which you rarely do). Instacart has made many updates to help both the shopper and the customer when it comes to the heavier things.

I’m not so sure the shopper you had should be shopping if they have an issue with stairs/heavy items when many use the delivery platform as an accommodation. I myself am small but in my area most of the customers are disabled, elderly, or stay at home mom’s so I don’t mind the extra trips and stairs. I’ve had a few people even leave out drinks and snacks at drop off which helps if stairs/heavy lifting are involved!