There are 2 problems with opera.
One has to do with the style of singing--some people just hate all that booming and screeching that goes on. These people should just get over it. Besides, miked crooners are just not that wonderful.
The other problem is the plots. From a modern perspective there just aren't that many great opera librettos. There is a book called Opera as Theater where the author writes long essays on the most theatrically significant librettos: Figaro, Don Giovanni, Fidelio, Carmen, La Traviata, Otello, Tosca, Turandot, Meistersinger, Rosenkavalier. Tell me and be honest: how many outrageous productions of these operas have you seen? Peter Sellars translated all three of the Da Ponte librettos to modern times. He had people shooting heroin in Don Giovanni, as I recall. But generally speaking these aren't the operas that get the bizarre treatment.
It's easy to make good theater of these operas. The problem comes up primarily when translating less successful librettos to the modern stage. Production designers are basically giving away the fact that they don't see the relevance in these pieces. They want to impose relevance, to drag the opera kicking and screaming into the present. Sometimes they succeed but more often they don't.