Just because you're young, doesn't mean you can't have range. Range doesn't mean a higher or lower pitched voice. It could mean that one is raspy, one has an accent, etc... just something that makes it different form the other voices. Of course as your voice matures, it may become easier to do this, but until then you have to make due.
As far as quality is concerned, it is important, especially professionally speaking, but most people on this site are not professionals yet. They may not be able to afford the best equipment so therefore it is unfair for us to take a lot of points away for something that isn't really in their control.
Finally, you mentioned how the others used immature humor, and whether you think it's funny or not, it had no affect on the score. I'm assuming that by this, you were talking about the writing aspect. By writing, it was important to have structure to your skit rather than have it be all over the place. The content didn't really matter. Also, writing wasn't very weighted either.
Overall, I'm sorry you don't agree with our opinions, but that's how it is. Simple as that. It's great that you have so much pride in your work (and you should. It was really good) but it just wasn't as good as some others and didn't quite meet the criteria as well as it could have. One thing that you should take into consideration, if nothing else, is that by being defensive and complaining about the critiques you're getting does not look good on you. Producers on here and especially professionally, if you're looking to go that far, will not stand for that kind of behavior. Most producers would rather work with someone willing to take critiques and direction. And the voice acting industry is a very close knit one, so when you're reputation gets out in a bad way, you won't be landing many roles.
Again, I really do hope you end up at least considering these things we're telling you, because you have a lot of talent and I'd really like to see you enter future contests to see how your progress. If not, then good luck to you with everything else that you do.