Out of my league 

vs. 

Not my league

The difference brings so much clarity. 

Out of my league means you believe in your own stuck-ness, that there is a better league but yours is inferior, that you do not belong there, that you are swimming way in the deep end.

Not my league means you have chosen your league and are perfectly content that your league does not include everyone, that you do not need to be part of the in-crowd to matter.