Was? So what happenened, where did it go, why isn't it still filing the role you are aiming at?
Another example, held in somewhat better regard by programmers, of a phenomenally successful tool that let end-users build working programs, is Hypercard. Which definitely isn't around anymore.
Looking at the prior art of tools that have succeeded at letting end-users build programs is probably a good bet. What they did right, what they did wrong, why they don't exist anymore even though they were succesful, if they don't exist anymore.