Romberg was not one to pay attention to words. His focus was on music.
Most of the plots from old musicals are pretty lame. That's true of opera as well.

Fortunately there are notable exceptions from Rome, Sondheim, Blitzstein,Rogers and Hammerstein, Yip Harburg, and others who write the lyrics and for those who are the unknown book writers of their musicals. From Boito forward, there have been great book writers for some musicals and operas..

The book is the heart of the musical. If it creaks, the show creaks historically.

The songs may justifiably outlive the show.