“Nero was dead when Revelation was written.”
Yes, but the preterists have any number of other reasons why they MUST date the writing of Revelation prior to 70 AD, so this fact won’t deter them.
To fit all the Nero theory it would have to have been even before then. I've read Gentry's case for the early date of Revelation and I don't find it persuasive.
in fact, even if it was written after 95 AD, it still talks about Nero’s fall and the time up to Titus Flavius Caesar Domitianus Augustus