I disagree with that statement. I think musicals can enhance the scene rather than take away from it. For example, in les miserables, when Fantine sings I dreamed a dream, so much passion goes into that song that she makes the something terrible that happened to her and twists it into something beautiful and emotional. Sure you can say that non-musicals can make you emotional, but can they make something ugly into something beautiful?
That is my point. There are some scenes that need to be ugly and gut wrenching. With a musical it glosses over that aspect. In most cases I have seen the musical aspect takes away from the plot greatly. Also as I said it makes it all less serious. If someone tried to make a musical out of great movies like Fight Club or Pulp Fiction you wouldn't be able to take all of the darker aspects as serious as you would if it were not a musical.
That's probably because those action movies were not made to be musicals. I'm not saying that normal movies are bad. All I'm saying is that I'd prefer musicals over non musicals. If say frozen was turned into a non musical, it would be boring. Any musical turned into a normal movie would be boring. If les miserables was turned into a non musical, it would be terrible. The music in musicals enhances the scene, not takes away from it. It's like when in some movies the theme music is playing in the background, it enhances the scene. I think that the music in musicals portrays a message that can't be given in spoken word. You can't replace a good song in a musical. I mean, why do you think everybody wants to go to Broadway a one point in their lives? Is it because they want to see a violent action movie? No! They want to see the best kind of play. (A musical obviously)
I see. By preference you prefer it, however that alone doesn't mean they are better. Yes frozen would be boring without the music because it is a boring movie. While it comes down to opinion, if we look at the top grossing films most, and critically claimed films most are non-musicals. Again you said it best yourself with Frozen, musicals use the music as a crutch for what would be a boring, bland film.