To me, the dealbreaker is the fact that it's a percentage-rate fee as opposed to a flat-rate fee. I was able to justify spending extra for Google Express as long as I made a large order.
With Instacart, the pricing is extremely blurry with an added-on fee of ~20% or so. I can't justify spending $20 + 20% on groceries. I might as well as just order out every day.
Maybe I'm lucky that I live within walking distance of a grocery store, but I'd be hard pressed to pay anything more than $5 for someone to drive my groceries to me. I could afford to pay for it, but if I kept that mentality my finances would die the death of a thousand papercuts.
With Instacart, the pricing is extremely blurry with an added-on fee of ~20% or so. I can't justify spending $20 + 20% on groceries. I might as well as just order out every day.