David Benedict defends the genre:
What thrillers did for fear musicals did for happiness. But 20th-century culture was all about lionising isolation, fracture and breakdown, so happy endings and happiness itself were all but banished from serious consideration. What place, then, for [Gene] Kelly’s rain-soaked jubilation or [Judy] Garland’s pleasure? Or the rip-snorting “Barn Dance” in Seven Brides for Seven Brothers or Ann Miller, tapping fit to burst and extolling her lust life, in “Tom, Dick or Harry” in Kiss Me, Kate (in 3D, no less). Freeing themselves from the constraining expectations of naturalism, those moments embody the culturally confrontational fact that compared with all other art forms, musicals have the greatest vocabulary for sustained joy.
Must be all that subtext.