Perhaps Chesterton had an off day

Chesterton had ideas about Gilbert and Sullivan, which might interest someone curious about his ideas about satire. Somehow, though he calls their works masterpieces, he seems dubious somehow:

For instance, in some of his best operas, notably in H.M.S. Pinafore and The Gondoliers, he seems obsessed with the notion that there is something very funny about the idea of two babies being mixed up in their cradles, and the poorer infant being substituted for the richer. But there is nothing particularly odd or original, or even amusing, about the mere idea of a substituted baby. That baby has been a stock property of many tragedies and numberless melodramas. To blast it with a yet more withering bolt of criticism, it has even happened in real life.

I've read The Bab Ballads, and not found myself returning to it. Perhaps that's a defect in my appreciation, but I think Gilbert did better work with Sullivan than alone.