Hello, just a question pertaining RPG's in tumblr, this is the first one I'm into in a long time, and I've noticed mods often save good characters for themselves and like don't even post them for other's to try and apply, they post the bios when they are already taken by THEM and rule out anyone who might have tried for said chara, my only question here is if being bothered by this (even if I don't even want said chara) makes me petty or is it justified anger?
Honestly, that's just them making their own space and playing the characters they're excited to play. If you're unhappy about it, you can make your own roleplay. It is a little silly to feel angry because someone on the internet developed a character/world for them and their friends with an invite to try out some minor characters and see how you fit in. You could always take those characters and make them well-written and amazing. You have no idea how good they might be under your guidance without trying!
If you feel strongly enough about it, you're always welcome to develop your own characters and world and roleplays. I know it sounds like a lot of work, but in the end, that's why they get the good characters. They did all the work to get where they are. You're not entitled to be part of random roleplays just because they exist. They aren't spiting you, they don't even know you exist. They're planning a fun party together, and you're standing outside the cafe seething because they got the cake they ordered ahead of time custom made for themselves.
Many times I see a fully fleshed out character in a roleplay application process it's because someone made them that way. They didn't come out of the keyboard as the perfect awesome character they are. They were just someone's pet project they put a lot of time and effort into. So they might appear to be the best character, but that's because someone loves them! That means any character, even the weird guy with only one line is capable of the same thing. Don't be afraid to try for a nearly empty character sheet, it's not a bad character, it's an opportunity to make a good one. The freedom to adapt and change them to suit you, and really express yourself. Once you love them, they'll become a good character too.
Hell, their characters may be from another roleplay entirely, just changed a little to suit this one. Imagine playing a character for years, moving them to a new RP, and someone you don't know gets mad because they wanna play your character. Kinda... weird right? And they wanna apply to take your character away from you? I'd be wheezing at the audacity.
So, my advice to you is to let that grudge lie very very deep until it rots into fertilizer, and the use that fertilizer to make your own garden to play in. Plant the seeds of character development and work on a character until it's a "good one" and make your own RP and invite people to do the same: expand on your world and make it even richer and cooler than it was when you started. It's a lot healthier as an approach, and you look 90% less like a fucko who got mad at someone for having fun the wrong way. Haha.