That 90%+ of the hiring signal can be projected onto "hours spent on leetcode" is exactly why this process has become a parody of itself.
We're irritated with the current interview practices, because the gauntlet that many of us have to run is not only wasteful, but it's also harming the profession. If one has to jump through the same old hoops their entire professional life only to be thrown out at 40, what's the point of building a career in software engineering?