I don't think this idea of leagues is the best model for us to have, but I don't think it's total BS either. For most guys, good luck picking up a supermodel. The competition is too fierce. If you're a Championship team trying to play in the Premiership, maybe one in a thousand you'll win by fluke, but the reality is you're not going to have much success overall.
The bad part about this "she's out of your league" business is that it implies that you shouldn't try and that you should accept your station. People aren't born into a league and destined to never improve. If you want to play in the Premiership, improve yourself to the point that that's where you belong. Get in shape, get confidence, get a good career, be secure in yourself. Believe you're worth the effort and act that way, and over time you'll get there.
A lot of people are happy to settle though. Often the "she's out of your league" business is judgemental - if a friend says that to you, he doesn't have your best interests at heart. He doesn't want you to make it to the Premiership, because he thinks he's stuck in Championship forever. He's projecting his own insecurities and limiting beliefs onto you and expecting you to live by them too. Screw that. Become a high value person and you will be chosen by high value women.
P.S. I don't know anything about football so Premiership and Championship are the only leagues I know.