I'm a programmer like you and used to believe in the idea that you should design in the medium which is HTML and CSS, and not in a tool like Photoshop or Sketch

I'm a programmer like you and used to believe in the idea that you should design in the medium which is HTML and CSS, and not in a tool like Photoshop or Sketch. But I've completely reversed my stance after working with a lot of designers who create beautiful sites that goes very well with the grain of the web. The reason is direct manipulation. You're not thinking in terms of the DOM's static flow when trying to create a design. Instead you want a medium where you can quickly transfer the idea in your head to a tangible form and try out different layouts, typography, colors, and visuals. But there still exist the problem of converting that design into code, and that is a wasteful exercise. You might have found Protoship UIPad, a tool I'm developing (in early alpha), useful there. It can convert Sketch designs into code - HTML/CSS and even React. Sketch has been incredible for that sort of stuff. It is a vector design tool and its design elements are fully expressible through CSS and SVG, unlike say Photoshop which is a raster tool.