You know how you can't usually write dialogue exactly how people speak because it comes out really annoying? Even though you're trying to depict truth, you usually have to do it a bit abstractly. It's lying, but they're small lies, right?
Okay, watch a dating show, read some looking-for-relationships-not-just-sex dating ads, then try to create some characters and not feel like a huge phony.
Almost a decade ago, I was totally addicted to those dating reality shows. Blind Date is the one that really comes to mind. And Singled Out on MTV. What I loved best was when these people would describe themselves. Now, these people are extroverts, obviously. So they usually said things like, "I love having fun. I love partying with my friends and being spontaneous. I'd like to meet a person who likes to have fun and go out and laugh and have a good time."
Holy shit. If I watched a Blind Date marathon, by the fifth episode I wouldn't know if I was going to laugh myself to death or kill myself to death.
But that's only the jerks who try to get on reality dating shows, right? What about the average person?
You used to be able to see how the average person saw themselves on myspace. One place that you can still get the experience is a dating website. I cruise them, looking for someone to replace my wife with, and then I kneel at her feet and slather them in kisses that I'm with her and not some woman who likes "to have fun. That can mean getting spontaneous at a club or spending a quiet night watching movies. Wants to meet someone else who likes to have fun. Enjoys movies and walking and listening to music and" hopefully getting spade and neutered goodgoddamn!
So how do you justify writing interesting characters? Sure, you have to give the reader a reason to prefer reading your book to just living boring life, but writing phony characters isn't the way to do it. If you can't believe in the characters, you can't care about them, so you can't care about what happens to them. So while I enjoy writing over-the-top characters, I wouldn't want to do it all the time.
And a writer doesn't have to. Because while people seem entirely shallow when they describe themselves, it's because the average person isn't introspective and doesn't know much about themselves, or if they do, how to transmit that information. As a writer, you get to use perspective and epiphany and whatever to take the boring, average person and give the reader the best of the character. You get to give everyone how the character sees themselves, consciously or unconsciously. Which is pretty cool.