The answer to your question is "you don't". You can't keep a competition fair.
I was in a high school theatre play where there was a winning play chosen out of all the end-of-year plays that I worked my ass off to play the past and I played it really well. I figure out that one of the judges didn't vote for the play I was in because they had some personal vendetta against it i.e. "well I remember doing that play when I was in school and... I didn't ever really like it" so regardless of talent that was in the play, she didn't "wanna" pick that one so she didn't.
Every competition is the same. People aren't gonna pick which cosplay entry is the smartest or most personalised or has an amazing wig. I really WISH they would but they won't.
That's why I cosplay purely for fun and, as you said, because I like dressing up as and emulating characters that I feel a connection to. I do the same with drawing; as soon as there's competition or profit in it, it's not fun anymore.
Maybe that's it. Cosplay is supposed to be fun, not super competitive and making you feel bad that you may not have the money or time to put together a professional-looking cosplay
I made my first attempt at cosplay last week, and I avoided the costume contest that day. Yes I like to applaud cool costumes, but I don't like the idea of turning around to people and say "see that, this guy is better at this than you." It's a bit too competitive and dispiriting for my tastes.
I also didn't join because I went as Matt Murdock, and all I did was colour some sunglasses and wear a suit.