I once knew someone who had worked in financial services for a few decades, and yet, had practically zero understanding of finance. I never got a sensible answer to any question from him.
I used to wonder, how did he survive for so long? Also, more impressively, how did he manage to learn nothing in a few decades?
With some benefit of hindsight, here are my postulates:
Humans hate offending others, and hence don't want to disturb the status quo. E.g., we will never hire a bad candidate, but if the same guy gets a job somehow, we will let him just be. Why be the villain? After all, the salary is not paid from our pocket.
Often, incompetent people even get promoted because who wants to deny them promotion and face unpleasantness? Why not just take the path of least resistance?
Experience delivers learning only when combined with curiosity and humility to learn. A sponge will soak more water in a second than a stone in 10 years. Experience does not equal knowledge.
As a result, in some companies you will find the best talent at the entry or mid-level, and a fair bit of dead weight at the top.
Experience without learnability only gives us grey hair. As we get older, we better have something to show for all the years.