Weird Al is a talentless hack who just makes lame jokes using other people's work. Literally doesn't make any thing orginal himself. There's some who are worthy of being the modern day mozart and it's sure as shit ain't weird Al.
I wouldn't say Weird AL is a talentless hack but you are right, he plays other people's music and not known for anything he's written. It's not fair to compare him to a composer. Weird Al is more like a member of the orchestra.