The first opera does not have to represent opera in general. I am totally confused by your response.
Especially "it is probably a better choice for a first opera compared to Berg's Lulu or Wagner's Parsifal but not much better."
That is only one person's opinion. I like Lulu and Parsifal, but it would be wise to listen to the several times first.
Also Death in Venice in a novella so one can read it before seeing the opera. Granted it is not an easy book to understand -- but that is sometimes true of Nobel Prize winners in literature. The Magic Mountain is Mann's great novel. It is of the moment now because the setting is Davos Switzerland.