I and probably everyone who has ever talked to investors/VCs had a similar experience to yours. And from an Investors standpoint it does make sense to basically ignore the product. Even though that can be frustrating. I think the pitfalls and traps that came with the interviewers questions have been discussed already. You know what they want to hear so naturally you are going to do better next time.

Anyway by all means there was good advice on here but don't get discouraged if you are passionate about your product. Because that, beside product and Team and everything else, is still the most important factor in a startup imo.