I agree with this perspective. However, you have to wonder why we don't have more Alexa skills in the platform. Here are a couple of my thoughts.

1. They require you to say "Alexa, tell <app_name> to <do_something>"; This pushes all 3rd party services one level deeper.

2. Amazon competes with too many companies and services these days. Instacart devs won't want to work on a skill within a platform that is itself is a competitor.