Coming up with that visual language is more work. Typically companies like to be unique (but not too weird) so while you can identify "best practices" among larger brands, most of your time is identifying what makes them different, and finding the best way to highlight those features visually. There tends to be some back and forth with this, and there are a lot of feelings to navigate, especially if the customer has strong preferences about how things look.
Color, layout, heirarchy, history and perception are all part of a good design education! It's worth your while to find art and artists that you like, and find how they solve problems. Paul Rand and Massimo Vignelli are two significant personal influences, and they have written extensively (or had things written about them) about their process and thinking.
(Edit: I spelled Massimo Vignelli's name wrong, oops)