Can someone tell me why they believe Janis Joplin was considered to be such a genius or a god?

I have heard people call her as much, and yet I have seen no evidence. I have only seen video and film of a drugged out, extremely homely woman who made herself that way, a woman who could not sing (especially not the blues), a woman idolized for I know not what. I've read her quotes and they are meaningless drivel. OK, go ahead and like her music if you want, but why build the waste case up into some sort of god? That's the sort of creepy hero worship mentality that cripples our minds.