Why no modern-day equals to ‘Carmen,’ ‘Tosca’?

[SFGate.com, 2 September 2010]
Dear Mr. Kosman: How come we don’t have any modern opera composers that approach those of the past? When you hear “Carmen” or “Tosca,” you can hum the melodies of those compositions, but I dare anyone to hum the melodies of anything composed after 1930. It would be so nice to hear a new “warhorse” opera. Where is the modern-day version of Verdi, Wagner, Puccini or Bizet?