Correct, they are paying for work done by people in other roles, who's title isn't UI or UX designer. It's on the backend person for velocity, it's for business development for leverage, it's on data scientists for insight, it's on logistics for convenience. Those people will be paid for solving those problems, not for tweaking CSS. My team, who falls into this category of more invisible work, has not hired UI or UX person at all. Which by mathematically speaking by default, is simply below the average rate for that work. Meanwhile Apple will pay easily mid six figures for someone in a more flashy role.
Design is much harder for power user tools compared to consumer. There is far more complexity and the expectation often is users must be trained to even use the tool.
Design only goes so far.
Describe the idea of what you want to do, not the inscrutable steps the application requires to get there.
Why ? Since its so notoriously bad why have there been no attempts to improve it ?