Ideally, the grocery stores or Instacart will add this functionality so it's baked in to the pickup experience. I honestly wouldn't mind if they did that and effectively forced us to shut down the app. This is a feature they should already have! And there are a lot of examples of people making something that's effectively a feature for an existing product, and that existing product building it.
The selfish route would have been to keep this to ourselves. We talked through the ethical implications of this and decided it was better to make it easier for everyone rather than just us. If everyone uses it and is able to grocery shop less often because they feel less food stress, things are improved.
We also purposefully don't support delivery slot since we think those should be only for people who can't drive or don't have a car, and delivery is more risky health-wise for delivery workers (who may have to visit 10+ different stores in a day).
There are definitely equity issues though. We've considered adding a prompt for people to donate to World Central Kitchen while waiting for a slot, for example.