As for the semantics, you are correct, we are not proposing that you can use Cosmic to connect to your WP backend. We provide a light-weight solution to add dynamic content to any website or app. We offer a web dashboard to create content and API tools and resources to integrate content into any website or app. No infrastructure management needed. Our customers benefit from using Cosmic because they can avoid the pain of building and managing their own CMS infrastructure. But if you need that level of control and you like managing infrastructure, that's fine, then you may not be a customer.
We are seeing more and more services that offload these non-core infrastructure services: Stripe, Twilio, Algolia. They add value to development teams that do not want to manage infrastructure. That's our opinion on how content should be managed.
Hope this helps see things from our perspective. And I have taken your feedback in a cheerful spirit, as I hope you have taken my reply :)