I think this article misses a crucial point with it's phrasing, or construction of the "design vs mathematics" tradeoff. Mathematics is superior for underpinning programming languages because it is universal. Design, like art, relies on a shared view on the world to be appeasing. Design from the 70's, or 80's is often unappealing to modern viewers because of the lack of shared experience with the designer, for example.

Mathematics solves this by appealing to a shared underlying "truth", that allows not only programmers with different backgrounds, but also computers to understand and process a programming language.