For anybody interested -- email is in profile. Happy to give you a sneak peek!
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.
I'm honestly more concerned with maintenance costs more than building costs. In my experience the cost of the alpha release goes down with visual editing, but the cost of subsequent releases ramps up over time.
People were saying that 10 years ago, they were saying it 20 years ago, the general attitude was even the inspiration for COBOL (that business people could write their own apps). Every single time it ends up being a disaster when it comes to slightly non-trivial use cases.
It's been tried and failed by companies large and small for decades. So what do you know or do differently that they didn't?
For example what I did was to code a server part in golang and use vue.js on the frontend and for the app builder. Using the web-based app builder (also 100% vue) the user can design forms. The forms are stored as serialized JSON in the database and the server renders dynamically vue.js components. It's super fast. And there's a complete freedom to design any form with a 16-column responsive grids and a lot of widgets and styling options. Forms are also nestable (thanks vue!) and completely extendable with custom JS code so it's possible to create a custom widget and then simply import it in other parts of the app.
As I said I think the shadow DOM and frameworks like vue really made the difference. I started without using such frameworks and it was not only tedious, but the resulting app wasn't very interactive and felt like a customized Excel spreadsheet attached on top of a PostgreSQL database. Now it's a completely different story - it's easy to build fully reactive apps that feel like a "normal" cloud app and are actually pleasant to use. Of course instead of spending few months designing and building it, it was created in a few hours.
So yeah... I think that drag-n-drop builders are definitely coming and will probably eliminate the need to write such apps in coming years.