The thing with vague requirements is that the real problem is that making decisions is hard. There are always tradeoffs and consequences. Rarely is there a truly clear and objective decision. In the end either you or the LLM are guessing what the best option is.
Yes, decisions are but they need to be made. Ideally shareholders will be given as much context so they can decide. This communication is as vital as having good programming skills imo. Your beautiful code means nothing if it does not adequately solve the business problem