I respect your opinion. However, I found Days of Wine and Roses to be a powerful, uncompromising musical drama with heart wrenching performances by James and O'Hara and a very fine score by Guettel. However, it's more of a chamber opera than a traditional musical. The solo numbers by the two leads are similar to arias and not for every taste.
I share your enthusiasm for the Light in the Piazza score which is more accessible to a larger audience than that of Wine and Roses.