You have to establish a lot in your opening pages. Characters, setting, relationships, the inciting incident and, if you're writing fantasy, another world. So, sometimes, it feels necessary to take short cuts. You need people to feel sympathy for your outcast character? Boom! Stereotypical bullies donning football or cheerleader uniforms. You need your character to look like they have a life and friends outside of the plot? Boom! Stereotypical funny, out-there, but supportive best friend who is mostly there to be your character's best friend.
I think its hard not to fall into stereotypes like these, especially in YA. Parents that don't understand, bullies, cool best friends. These are tropes that have been done to death. So if I start reading a scene the features one or more of these, the story starts to feel tired. I feel like I've read it before. And you don't ever want an agent to feel like they've read your work a million times before.
There are a lot of ways to solve this problem. You can spend a lot of time developing your side characters. You can pull the reader through with a gripping voice. You can try starting your story in a different place to see if it cuts out the stereotypes. Experiment and you'll find a way.
Unique openings are difficult but they can start with unique, fully developed characters that don't take shortcuts and draw in your reader from page one.