But that's only because they're so close minded (and apparently many of the fans are too).
So, Dracula can return once every 100 years. Let him then, there are many other vampires that can serve as the main villains in those periods. Vampires like Carmilla, Olrox, Walter (well except he was absorbed but still), Joachim, Bathory and others.
Death could also serve as a final boss too with a bigger role than "ok, I'm done. go kill him, guy who didn't even appear until now".
Then we also get the whole cults that are the main villains (and as usual are eventually shoved aside to throw in a pointless Dracula battle)