I partially agree with you, but additionally there's a whole set of employees who would be clearly redundant in any given company if that company decided to just use a simple, idiomatic, off the shelf UI system. Or even to implement one but without attempting to reinvent well understood patterns.

One reason so many single-person products are so nice is because that single developer didn't have the time and resources to try to re-think how buttons or drop downs or tabs should work. Instead, they just followed existing patterns.

Meanwhile when you have 3 designers and 5 engineers, with the natural ratio of figma sketch-to-production ready implementation being at least an order of magnitude, the only way to justify the design headcount is to make shit complicated.