What Wobbles said is very true.
For example. I play an amazing spacing game. However, I am also not patient, so if I play someone who is willing to wait, I often will be the one to approach, and since I am not as good at that, I do a lot worse.
If someone is more aggressive, I am used to it and can handle that.
Part of the reason I developped this way is I never really played the top tiers much throughout the years. This meant that I was often on the receiving end of their great pressure game. Hence, I developed my game around a defensive game with little risks.
I would say lots of Mid level players could be high level players in certain situations.
Oh and another thing. For me personally, since I was so good at spacing, I never really needed to roll or spot dodge. This is actually a BAD habbit for me that I would have to break if I wanted to be a top smasher. There are certain situations in smash where rolling and spot dodging are very helpful. In fact, many people will eventually, and usually subconsciously, take advantage of the fact that they know I will not roll or dodge.