As a writer you have to be aware of things that will put readers off. The list of such things is long and ever changing and some of what’s on it is easily avoided. One of the things that most annoys readers is the use of a certain phrase. This over-used phrase is used as a hint to establish the “uniqueness” of the main character, but in actuality leads the reader to believe the story’s going nowhere good.
“She/he was not like other she’s/he’s” is a commonly used phrase that grates on the reader’s last nerve. What’s wrong with this phrase? The author is trying to establish that the character in question is different, but this isn’t a good way to go about it. It’s not bad just because it’s an over-used phrase, it’s bad because it’s insulting. Inevitably there will be someone (many someones in reality) of said gender who do the thing that makes them unlike others of said gender. All this phrase does is foster stigmas and stereotypes: He/she is better than other he/she’s because they do or don’t do this; he/she stands out because they do something most other he/she’s don’t. This plays heavily on gender stereotypes. Nobody wants to read a sexist book.
Readers want unique characters, but the idea of a character that is different isn’t about the character disliking or liking something most others do. That’s missing the point. It can be about the feeling of being different, of the character not fitting in or feeling left out. It can be about wanting characters they can connect to. It can be about character’s that are from demographics that are often neglected. When they say they want different characters they mean they want to see a female lead, or a lead who isn’t white, or a lead who isn’t straight, or a lead who’s transgender. They don’t want to see a character who is different because they’re male or female and they wear glasses and like comics and read. Newsflash: lots of people do those things.
There are plenty of ways to establish that you have a character in possession of unique traits, or who is a bit different. The easiest way to do this is to simply write your character. Don’t try to sum them up in one line, or in an opening paragraph. Let your character come to life over the entirety of the book. If your character or your story is about being different, or the notion of feeling different, then it will come across in the story. If you tell it properly.