I don't think a unique idea is necessarily required for a startup. It could be instead that you've identified an under serviced market niche. This could still be a very good startup idea.
True, but your idea has to at least be good or relevant, which OP's unfortunately wasn't. It doesn't take some weird emotional outburst to stand out, it takes having an actually good idea. Of course you need to convince them it's a good idea, but again you don't need an emotional outburst for that, if it's an actually good idea it should not be difficult.
In this case the emotional outburst suggested the founder might be in such close contact with the problem that he might find better solutions, and will likely recognize many non-solutions before wasting time on them.
At least that is a takeaway I would have.
It is not everything a VC might want to hear, but it is a positive.
You can spend so much time on something, yet it wouldn't tell a YC interviewer that it's a problem you're intent to solve.
Case in point, my YC idea. I spent loads of my free time on building a MVP, got praise for it, but I did not have a burning passion to solve that problem, or even any desire that I wanted to be in that space long term.
What startup has a truly unique idea? Doing the same thing a hundred other companies are doing and being slightly better and luckier is how most of them got successful.
You could have a unique idea that isn't shit. If you can't have a unique idea that isn't shit, you shouldn't be a startup founder in the first place.