Design does not equal development/production. An architect or product designer using CAD designs the building or product, but they don't actually develop/produce it.
I've never seen a good design program produce good code. There are simply too many variables to accout for. Likewise, something that produces code general is either hard to design in or is not good for design.
What's the point of a design only tool? To show a developer what they should build, like plans tell a construction firms what to build.
I completely understand the desire for a design app to be able to produce a website or app, it's just easier said than done.
Adobe Certified Expert & Instructor at Noble Desktop | Web Developer, Designer, InDesign Scriptor