I understand what you're saying, however, I think that a lot of the criteria used in these homework assignments can instead be worked out via some conversation to judge the depth of knowledge and culture fit.

I've passed tech interview challenges only to fail the culture fit because I thought it would "be so easy" after the tech challenges.

And I've passed culture fits only to fail the homework assignments.

In one circumstance, not realizing that a separate recruiter was sending me to a company I had previously interviewed with, I've also seen previous work that I did in a homework assignment, given to me in a different homework assignment with a "what improvements and features would you add to this solution?," when the original homework assignment was the same task. That was a major blow, and gave me feelings they were using some of that work internally.

I get that it's extremely expensive in time and money to hire the wrong person.

On the other end, it can also be extremely expensive in time and money to not be extremely selective of whom you want to work for.

lmao do I understand correctly that you were given code that by chance you yourself happened to have written and were asked "how can this piece of crap be improved?"

It had work in it that I put in before, but it wasn't entirely all mine, nor did it have all the original work I put in the first time.