Jessie, a note on Wagner taking longer to write his operas, he actually did exactly that after the release of Das Rheingold and Siegfried.

The themes are still somewhat palatable to a modern audience, though they are a bit dated in their motifs, and a lot of Americans are not familiar with the Germanic and Norse mythology. However, the idea of class warfare today was largely built in the mid-late 1800's and so we can all kind of understand the concepts being expressed.