That's why I don't target primarily developers, but the end-users of such apps. Of course knowing Javascript wouldn't hurt, because it opens a lot of more possibilities to further extend the entire app, but my idea was to make it possible even for non-developers to create apps for CRM, invoicing, accounting or inventory management for their needs. So in my case it's not really visual programming, but a drag-n-drop builder, which also has an integrated code editor in case the user needs it: if they know SQL, awesome - write a custom SQL and it is automatically mapped and available in the forms.

This sweet spot that you talk about between ease of use & flexibility is definitely key.