I don't think ruby is the one to blame. It is very flexible. With the possibility to write ruby extensions in c/c++, on a Windows PC, one can also write it in C++/cli. Thus one can easily integrate any .net stuff. If one do not like webdialog, any other gui library can be linked through the extension. E.g. one can build c# plugin via p/invoke [DllImport("msvcrt-ruby18", CallingConvention = CallingConvention.Cdecl)]...
For stuff like Visual Programming the most challenge thing is parametric model. In sketchup this is not easy, since entities can easy be manipulated. I mean e.g. if you simply delete the area of a face, it becomes 4 lines. The entities are not consistent. They are so flexible. And if this is not a issue, one can make some effort and create a Visual Programming interface for su.