On one hand this demonstrates that it isn't useful for testing innate skill.
On the other hand, it was the best paid work I've ever done. It was an essential part in me getting a job (not at Meta) that paid multiples better than previous roles.
This work allowed me to place myself in a group of people who can pass the test. Some of the people who are outside this group would make fine employees but don't want to or think to put in this work, for understandable reasons. But all of the lackadaisical applicants will fall outside this group. I get to signal that I'm not one of them.
I spent 4 years in higher education for a non-essential positive signal to employers: 2 weeks is nothing.
In the past I hated Leetcode, now I've begun to think of it as an opportunity. While as an individual my opportunity to shift the consensus on this form of interview is low, my opportunity to benefit from the arbitrage is high. Don't hate the player, etc.