95% of the information on the web is written language. It is only logical to say that a web designer should get good training in the main discipline of shaping written information, in other words: Typography.
Building structure requires serious listening, serious reflection, and serious imagination. All this requires experience, and no matter how experienced you are, it costs you. We spend our time and nerves to save users their time and nerves. Well-designed things give us the invaluable present of time. Well-designed products do not just save us time, they make us enjoy the time we spend with them. They make us feel that someone has been thinking about us, that a nice person took care of the little things for us. This is mainly why we perceive well-designed things as more beautiful the longer we use them, and the more used they become.
No matter how many screen sizes our artboards account for, some user’s browser will break loose from our prescription. With users resizing, rotating, and zooming the screen, new devices stretching, squashing, curving, and cutting (e.g. the speaker area in iPhone X) the screen, the sizes become infinite. Good luck making an artboard for each one of them.
Artboards are a lossy format. Using artboards in a handoff is a lossy process. When we pitch a finite number of plans against an infinite number of situations. We inevitably get in-betweens. Once there are in-betweens, there are unknowns. Once there are unknowns there is guesswork. Once there is guesswork, there are surprises. Engineers take the path of least resistance. We are ones who paved the path.