What you're saying is reasonable, and there are lots of people attempting to make RAD systems. Unfortunately, they always place severe limitations on the kind of software that can be created with them, and hence none of them have become particularly popular.
It seems that there's something missing from all the existing implementations of your suggestion. Perhaps it is that the UI and data flow primitives that we have aren't flexible enough to express a lot of business models, thus requiring custom implementations.
Delphi, Visual Basic, FoxPro and Access were all extremely popular RAD tools exactly because they made creating a certain class of systems extremely easy.
I had the misfortune of using Visual FoxPro once upon a time. It was horrifyingly bad, but perhaps by that time (2002-2004) it was suffering serious impedance mismatch with the rest of technology which had moved on. Anyway, I wouldn't call it a good example :)
Regardless, that was kind of my point - all these systems are only good as long as you stay within their constraints. The unfortunate thing is that the constraints always end up being way too tight in practice.
It seems that there's something missing from all the existing implementations of your suggestion. Perhaps it is that the UI and data flow primitives that we have aren't flexible enough to express a lot of business models, thus requiring custom implementations.