I agree with your latter point on system design. I've had 'big data' interviews where the 'big data' fits in the memory of my desktop machine - so I'm going to give you a very different answer to your over-architected hadoop cluster running over 20 1gb containers or something.
You have to make this a back and forth, not a monologue. Nobody is going to criticize you for tailoring your response to what they want to talk about. Treat it more like a coworker you respect asking you about architecture options, not like a right/wrong graded quiz from college or a chance to assert your knowledge and experience. Your knowledge and experience will show anyway.
I agree but it is not uncommon to find interview processes where a monologue is exactly what they expect and they are unable to have an actual conversation about the topic for whatever reason.
