I think the biggest thing here is, "What you’re looking for is a genuinely thoughtful response." If you are holding back a secret on how you'll solve the problem, and do get such responses; you'll hopefully know which it is.

If you are given that genuinely thoughtful response, it will come with the problems with your idea and the reasons that they think there are problems. You can then compare this information to your secret information. If the problems they present match up, and you have plans to solve them, that's great; if they come up with something you had missed, either a different reason or a widely different problem, you may need to rethink the idea.

Of course, this process isn't going to be 100%, and you're still going to have to some faith in that what you believe is correct, but it's a decent process to go through.

I also don't believe you always have to take the non-obvious route, it is just likely to have less direct competition and a higher risk/reward vs an obvious problem.