Why automatically ascribe bad faith to people who study for coding interviews? They went to all that trouble to get better at something, so they're obviously diligent and seek self-improvement.

> Senior talent doesn't have the time or energy to push back on all of a systematically incompetent person's code until it's good.

That sounds like a problem with the company's timelines or priorities. If senior talent is so strapped for time that they can't insist on decent designs upfront, then they likely can't hire the right people either. Because even that takes time and energy. Mentoring juniors is part of the job for senior engineers.