Playing a little Devil's Advocate here since I do go to the gym quite a bit to workout...
I think the problem here is seeing bodybuilding as the bridge to success with women.
It can be, and we are talking with only a certain percentage of women, but is by far not the only path.
Typical progression:
Guy is skinny, young, nothing much going for him in life yet -> works out, gets buff -> feels more better about himself -> finds out girls are more attracted to him -> reasons bodybuilding gets him girls
But if we look closer, it can be argued that it was his new self-image that he had of himself because he tasted success in one field only. In reality, that new-found confidence can come from many things. The mistake is thinking that bodybuilding is needed to be truly successful with girls.
Personally, if I had to do it all over again, I would have spent more time on my passions in life, instead of bodybuilding. Let's face it, bodybuilding takes up a ton of time and requires even more just to maintain. Unless you are going to reap huge benefits from it (financially or enjoying it so much that you are truly passionate about it), I believe there are better paths to take. Success in any field can breed the same confidence, and in turn, make one that much more attractive. So you have to choose where you spend your time wisely.
Looking back, If I had a chance to take all the hours I spent working on bodybuilding and put it in what I truly love to do with my life, I would do it in a heartbeat. Not only would I be more successful in that field, I would be doing what I really love... and if I achieve success, the confidence and new self-image of myself would be far greater than what bodybuilding would ever give me because in reality, I did bodybuilding for lesser reasons (to get girls, aesthetics, to be better at sports, etc.). Heck, instead of spending time bodybuilding, I probably would've gotten more success with women by using the time to just go out socialize with people. It's just that when we are young, we take the easy, less risky, rejection-avoiding route. If I get more muscles -> girls will flock to me. Look, bodybuilding there are no surprises and it's very straightforward while being easier to monitor progress. Bingo! Let's do that instead!
Like others have said... I have seen many many examples of skinny guys/average looking semi-fit guys getting gorgeous women in life. It also seems like bodybuilding is very popular nowadays, so being just a bit better than average may not make you stand out as much, if at all, especially if you lack social skills, style, or other fundamentals.