Earlier quoted context omitted.
engineering is about creativity and practice and not about memorizing standard solutions. leetcode does not test the skills that matter.
Leetcode is not for engineering on the job though, it's purely a test for getting hired. You wouldn't expect lawyers to take an LSAT while on the job. A lot of people, especially those who don't do Leetcode or work in a company that asks such questions, think Leetcode should somehow relate to the work and are annoyed, but it's just a test like any other.
It teaches you absolutely nothing about the rest of the job, around comms and leadership, which most of the time are more important than your ability to solve puzzles.
It selects for people who want to get in and want to grind.