The substitutions I've received have been reasonable but I do make a point of asking about prices because things aren't always a good (or even fair) trade.
One time, the product I had selected was on sale and they wanted to give me half the quantity of a different (but equal) brand that wasn't on sale. I pointed out the discrepancy and the employee was able to resolve the issue. But, I had to be paying attention to get this taken care of.
I prefer Doordash because the Dashers will typically interact with you enough that it's almost as good as being there.