Maybe I’m not good at the basics, but as an ostensibly quite successful engineer, I have rarely had to do “the basics” at work, and I don’t see how leetcoding would improve my actual performance.

Leetcoding is basically testing how well you can cobble together solutions out of a decently large bag of tools. You run into other tools you have to cobble together as part of actual work, but you never have to memorize those particular tools.

So leetcoding becomes memorizing an arbitrary feeling set of tools that you never actually have to use in practice just in order to prove that you can cobble together solutions on the fly using the tools.

Certain personality types bristle at being told to memorize a large set of things for no practical reason. It feels subservient to do so.

Now if what you are really saying is that forcing yourself to feel subservient is required in a lot of careers in order to succeed, then yes totally :)