If I was your coach and heard about you whining like the above post, I might not want you on my team for fear that you would complain about wherever I put you and bring the team morale down.
No one can make YOU look bad besides YOU. They can get under your skin and bother you, but only you can screw up yourself.
I would tend to think that because the girls said, "grow up, get over it, So immature!", that you vocalized your issues and were whining about not getting to hit.
I can tell you that that is the most annoying trait in a player. Volleyball is not just about hitting. YOU may have blown your chances by being a selfish player.
Imagine, what would have happened if you just smiled at the coach and said, while smiling, "I set last year coach, and I don't really feel it's my best spot, but I'll do whatever I can to make the varsity team."
You'd probably be thought of pretty highly as a person that would do what was asked of them so the team was successful. But instead, due to your poor attitude, you are going to have to dig your way out of the doghouse.
Now, there is a way out...
Forget about everyone else that is negative, you don't have time for them in your life, do you? Worry about skills, especially serving, that you and you alone control. Maybe you're not as good at hitting as you think, maybe your coach saw you setting last season and thinks you have a lot of potential at that position. Maybe if you DO get over it, you'll realize that the setter is the most important key to a successful team of hitters. Then, you can concentrate on being the best player you can be.
News flash: Coaches aren't stupid and they know the game and athletic abilities required for each position, even more than you do. You just might be thinking a little too highly of yourself. Truly think about it and I hope you take the high road to success.