Okay, here's the thing I noticed most, re-visiting THE VAMPYRE, being exposed to THE VAMPIRE and rediscovering DRACULA.
Polidori introduces the idea of a "gentleman vampire," one who walks among us, recognizable as a human. He stalks society. This works in Polidori's tale because we don't dig too deep. Ruthven appears, he's stunning, but when Aurbey spends an extended time with him (and Ruthven doesn't apparently spend too long in one place) he begins to become repulsed by his behavior, which is at first seen as merely churlish, not homicidal.
In THE VAMPIRE we have a "Rutwen" who is far too careless. Someone saw him die in Rome, another in Greece - he poses as an imaginary brother he doesn't actually have. This would confuse a simple person for a day or two, maybe. But it introduces the major plot hole in the gentleman vampire story; you can only get away with it for so long.
Anne Rice tried to deal with this conundrum in a rather Randian style by suggesting that mere mortals are too thick to notice what is right in front of them. Same guy never ages, disappears for a little bit, passes his estate onto his "nephew." No one, not the IRS, notices or cares.
Gaiman suggested the same thing in Brief Lives. I digress.
What Stoker did in the introduction of the character of Dracula was to address this problem by making the gentleman vampire from somewhere else, somewhere exotic. They know him where he comes from, boy howdy, the Transylvanian natives aren't stupid, they know evil when they see it. And this foreigner enters London society and fools everyone ... except the Dutchman.
What is up with the Dutch?
Even then, the ruse only lasts for so long. So the question remains, if the vampire originates in a certain society, the challenge in presenting a modern adaptation is making sure all the mortals don't come off as totally clowns.