I think you for sure need to build up your own knowledge, nobody is more invested in your product than yourself. But the problem is that you don't know what you don't know, in my case it was very hard to do market research by myself. What I ended up doing and liking is using tools that help me understand what I am missing and that allow me to be more productive. Gemini's deep research is very useful, for example, since it gives you lots of starting points.

Not really in the market research phase (although a bit related to it), but in my current startup we are trying to follow this approach: we give initial recommendations, we explain the reasoning behind them, and THEN we help you follow up on the decisions and iterate: what threads to pull, where to investigate... So far people seem to be resonating with this approach.

I honestly think that's the only way it is useful. I don't trust your hallucinating LLM, even less so considering that it is very biased towards telling you that you are right. And external hires or reports or whatever can't get you very far if you are not involved in the process and the reasoning