If you're just setting up a prototype environment then yes, sure, set up a VPC and go with the defaults and don't worry overmuch about what you're doing. However, when you start setting up a production environment, the story changes. If you're a developer creating network-facing applications, then I am convinced that at least a basic understanding of computer networking is not optional.

I think the attitude that not everyone needs to know these things leads to people mistakenly thinking they can always have them be someone else's problem which furthermore results (needlessly!) in brittle systems.

I'm not asking for every developer to become a networking expert, but learning at least the very basics about your dependencies (you depend on networking, after all) is what I think a professional should do.

To address your NoSQL example, certainly it can be convenient to prototype with a dynamic schema, but you as a developer should still understand that even if it is dynamic, your data still has a schema and a concrete structure, which will affect your application in various ways. For rapid prototyping it's fine to ignore all this, but again once you start thinking about production, you no longer have the luxury.