Hello :) "what a catch" can have a couple different meanings, that is probably why people have different translations for it. When someone says "What a catch", they are usually implying that something have is amazing. For example; "I have a girlfriend, she is beautiful, super intelligent and treats me great - what a catch!" In the song by Fall Out Boy, the singer uses that phrase in a sarcastic tone. He is trying to imply he isn't that great at all and not really much of "a catch" p.s- Please note that this term can also be used in sports. Example: "The soccer player kicked the ball and the goalie saved it, what a catch!"