design should be simple because if form follows function then a straight line is the shortest distance between two points however this doesn't apply to art because art has no function and to attempt to to formulate what art should be is asinine watch the movie "never look away" https://www.imdb.com/title/tt5311542/
There is the stance that design is the blurry line between art & science... given its a Wright quote, I'd say it's probably accurate to interpret it that way. He probably saw design as an art. Movie sounds interesting, thanks for putting it on my radar.
regarding design if you look at any big car company like BMW you will notice how their highest end product ( 7 Series ) has a simple and clean design inside and out https://image.nostr.build/1b3747e5330d676d0f024a9d4dc9cc4926ef28dd0eb603ab27f54f15bdd0daa0.png https://image.nostr.build/2af36f5321730a05e136e9ba65c2da3c703d1943039d278537bfae49ff2c26ab.png the lowest end product ( 2 series gran coupe ) is overly busy with a lot of unnecessary curves and angles https://image.nostr.build/2185e74fc91ba4e1c147f785cfabeba072c5a5da97f5a585b6f06a1c84ac41d8.png https://image.nostr.build/7f901d049957ad48eb15d135a66ec35105527796259d7089fadf59c4f3b8d2ec.png this is 100% deliberate and ALL automakers do it. for example Cadillacs follow the same exact pattern. it is also the same for things other than cars for example refrigerators. the most expensive refrigerators from a brand have straight handles. the cheapest have curved ones. and so on. "design" is actually just a scam used to ugly-up cheap products to make the expensive ones look better in comparison. nobody actually designs anything anymore. products are simply ruined on purpose to reach the target level of cheapness for any given price point. it is also the same outside of design as well. everything is ruined on purpose to make sure nobody gets something they haven't earned. average people have no clue about any of this just like they have no clue about anything at all.