That life no longer resides in the whole. After reading your first post, I thought about this passage too. Certainly, N used Wagner and Baudelaire to illuminate his notion of decadence, and he also saw the Romantic movement as a sign of decadence. I think that the notion of style and decadence cannot be separated.
Style is a symptom of decadence just as fever, migraine, and nausea are symptoms of illness.
Personally, I think that N's style is a bit decadent and that his style can be seen as a symptom of his decadence. N's apparently decadent style, like a seductive song, draws the reader in and then, bit by bit, reveals itself to be the very opposite. For this reason, I think N attracts so many decadent types. However, if one doesn't try to put the puzzle together, one will remain ignorant of N's ultimate meaning and consequently remain decadent. A decadent style grows out of a decadent garden, and since N claimed to be decadent, he could not help but have a decadent style.