When I'm interviewing senior candidates or being interviewed, my preferred first interview is a conversation about interests, past work, and areas of future work. Depending on the ability to communicate effectively and deeply about topics of shared knowledge and interests that will decide the next steps. It also gives a good idea of the candidate and the company in the process. The best use of time all around. I have yet to be 'duped' by an imposter by this process. Some may be slightly underwhelming but I've yet to regret a hire or being hired.

I do that as well and that still doesn't tell you much. It's a good first screen filter but isn't always sufficient. For senior candidates though, I agree that a homework assignment is not the best qualification process.