We are mixing aesthetics and stylizing with things like ui flows and product design. Just becasue it's called "Design" it doesn't mean it can only be done by people with "Designer" on their titles. It seems that the only reason we are separating "Development" as another dicipline incapable of doing some of the things we call "Design" it's because we don't call it "Code Design".
A visual designer is as capable of developing a useful and functional ui design as a developer. Even if one is called "designer" and the other is not. Stylizing is another matter.
PS: My point is that some of the activities we are calling "Design" are VERY different to some of the other activities we are calling "Design". We lump them together because, well, they are called "Design". But they are not equivalent, not even related really, or at least not more related that some of those "Design" activities and "Programming".
As a metaphor, Architecture is not Interior Design, nor is Structural Engineering. An Interior Designer, by definition, is as prepared to do architecture as a Structural Engineer... and even less so in some cases. But with the right training, both can become Architects. Or for an example closer to software, Game Designers come from a lot of backgrounds, from art to writing to technology. Their backgrounds affect the type of design they do and their focus (Jon Blow, for example, prioritizes the "mechanical" design of the game, while Edmund McMillen works mainly from an stylistic point of view), but all of them are doing great game design.