At this point, I'd like to pause. It seems odd that 'thinking about plays' and taking the performance of a play as the basis for study are especially bold steps. But they were. Before the Enlightenment, theatre was discussed either as scripts or subjects for censorship. Like, did you know that plays about religious subjects were more or less banned from 1600 onward in France and Britain? Racine did a few, but they were just for school productions. Those Passion Plays that were all the rage in medieval times were seen as an anarchic occupation of the Easter story. You'd think they'd be fine in Christian societies, but no.
I suppose the death of dramaturgy was bound to happen: as soon as performance becomes the focus, there are all sorts of ways to study it. It is easier to talk about dramaturgies these days - all different ways of thinking about, or making, theatre. So trying to hold a field of study that is so open was always going to be a tough call. If the Big Idea is... thinking. Well, that's blowing the whole thing wide open.
But this isn't what killed dramaturgy. The problems really start when they invent the idea of the genius. Like I said, the challenge was always going to be Shakespeare. How on earth can theory account for a talent like that?
Both Lessing and Diderot sussed this, and included a 'get out of jail' card. Diderot gave a good description of the genius. Basically, he said, certain people were too cool for school, and could do all sorts of stuff not imagined in your philosophy, Horatio. And Lessing agreed. The rules were handy for a hack, but the genius could really swing.
Before Diderot, genius was a spirit or something: the word comes from a Latin god, and they'd descend on an artistic for a bit, give them the good stuff, then disappear. The Enlightenment wasn't that keen on metaphysical fairies, so Diderot turned it into a personality type. It was someone who combined an extreme sensitivity with the ability to contemplate with detachment, who loved a bit of nature but knew how to communicate.
The idea of the genius turned out to be very popular with artists -even if it suffered a bit in the translation. And this is what did for dramaturgy... at least the first time.
Almost immediately, the status of the artist went right up. In 1700, Bach was a jobbing composer with a few good tunes. By 1802, he had a biography that treated him like a saint, including anecdotes about his mastery of the keyboard.