One of the important choices for a developer is to decide what not to drill down into. How text fills a space, why sometimes it looks wrong or how to make a paragraph stand out is clearly the province of graphic design.
Typesetters can also put space between the letters in words (hence the need for tracking) to enhance the effect.
Now from a design point of view, serif fonts look “old and established” whereas sans-serif fonts look “modern”.
A font engineer can look at the way a letter looks in a certain resolution, and realize that it needs adjustment.