It's tedious and a waste of time. Some people enjoy grocery shopping. Power to them. I hate it.
Online ordering lets me plan what I want to buy. This lets me research--and save--my preferences in a way that can't be done in the aisle. It also removes the after-work parade of junk-food temptations. Stores are great for sampling. I like shopping at farmers' markets because I can nibble. But for that purpose, restaurants and tasting menus are superior.
I don't use Instacart. But I love FreshDirect. Not only are their prices competitive with brick-and-mortar stores, their produce is fresher. When someone says "I want lettuce on Tuesday," they message their farms and ensure it's picked at the right time so there is minimal delay between harvesting and delivery.