That is because most of the “jobs” require just that skill or some other very limited skill.

I was asked to hand over the stuff that I was working on, when I left a job. It was interesting to find out the girl I was supposed to train, didn’t know even the absolute basic programming stuff. She had been in the company for five years and was well liked. She was doing just one specific thing all those years, and she was very good at it. She got raises every year, the company had a perverse interest in keeping her that way.

I have worked in a dozen places in my life. Though tall promises are made during interviews, not one of those companies gave a shit about employee growth etc. only way to do something interesting was to leave and find another job - rinse and repeat.

It is not just the employees fault their skills stagnate. Employers also contribute to it.

And how does CS degree where your learning just the Math Heavy theory do that? if you did an EE, Mech or Civil Degree maybe those are more appropriate.