I totally agree that system design questions can be silly sometimes. When I do system design interview questions for senior engineers, I ask a really broad and complex questions and let the candidate drive us towards the system. The point of the interview is evaluating if the candidate can complete those soft skills in a reasonable way. I try to answer basic questions such as these:
Did the candidate just go for design without asking questions?
What questions does the candidate ask?
What areas are they asking questions about?
Can they take critical feedback on their design well?
There is a little bit of discussion on technology choice, but typically if they can justify an out of the norm choice it is fine.