It's a great score, but you can't have the heroine die from heroin (!)--and then have the hero say, "Oh, well, I promised you a happy ending."
They thought that was being honest and true to life, but it just made for a bad musical.
I don't believe it can be "fixed," without changing history or changing the style of the score, which would be throwing out the baby with the bathwater.
And I agree with all who love The Grand Tour. That's the Jerry Herman score to revive!