How is it unoriginal? Artists are inspired by the works they read or see and want to adapt it for the stage.
Most if the time it features a completely new book and score.
Sounds pretty original to me.
You seem to think it's so easy to sit down and come up with a completely original storyline, characters, book and score.
You want it? You do it. It's not as simple as you think.
Most artists, whether they be writers, composers, choreographers or even painters are inspired to come up with their works by something they experienced in real life. They rarely sit down and create something out of the blue. Are you calling all of those artists unoriginal, too?
"I love talking about nothing. It is the only thing I know anything about." - Oscar Wilde