Yea, they’re pointless. The amount of time someone spends on a truly difficult and important problem is maybe 0.1% of their job. And usually it’s better to just call in a domain expert anyway if it’s something that important. The other 99.9% - do they show up on time and work hard, do they care about the company, do they fit in with the rest of the team, etc, mostly can’t be determined in a short interview anyway.