Honest question: did you really not read the room there? I mean, if I were on the interviewer side, asking that question, and getting an initial answer "Well, to be honest I would tell them to use GSheets because given the current situation is the highest benefits/costs solution, but for the sake of a system design interview I would also think about designing a bespoke internal solution that would use blah blah blah". You would get a "strong hire" evaluation and you would still be able to turn down the offer if you wanted because that question might have been a red flag to you.