Shakespeare on the operatic stage: Why won't it work?

One idea briefly mentioned in the article has caused me a lot of thought: Why was it that only one Shakespearean adaptation that used the Bard's language was successful? I admit that I am not particularly familiar with Britten's A Midsummer Night's Dream, but I do know the play. I believe that the best explanation I can surmise lies in that very source: the play itself.

In the article we read, Heyman states that not only was Midsummer the only successful adaptation of word-for-word text from the Bard, but that all of the Roman tragedies had proven infertile ground for opera libretti. I believe this is the result of a fundamental aspect of opera: opera is larger than life.

When I think of Egypt on the operatic stage, of course my first thought is of Aida, and specifically of a set for it which I saw on the stage of the Arena Theater in Verona, Italy. We were touring the Arena during the day while the stagehands were assembling the stage for Aida that night, and I was awed by the sheer magnitude of the golden sphinx and other statues that adorned the stage. While this seems to fit perfectly into the ideas that Zeffirelli had about Barber's Antony and Cleopatra, it doesn't mesh with the Shakespearean play that was the inspiration for Barber.

Shakepeare was deeply interested in the human aspects of his characters in the Roman tragedies / histories. Thus we see development between these great men and not only Cleopatra, but their own wives, too. You see this in both Julius Caesar and Antony and Cleopatra. The characters are more real, more life-like, than might easily be adaptable to the operatic stage. In contrast, A Midsummer Night's Dream deals with fairies, magic, transformation of a human into a donkey...in other words, wonderful fodder for operatic development.