Not convinced. What would happen in REH's ghostwritten novel Conan meets Dracula?
YMMV so if it doesn't work for you, it doesn't work for you. But here are some thoughts I have on this question
This is why the domain concept is so crucial, and why powers checks and monsters all being unique is crucial. Conan would likely find Dracula rises up and kills all his men in the middle of the night after he thought he had dispatched him already. In Ravenloft domain lords are incredibly hard to permanently kill (this varies of course as there is a spectrum). By extension so are even standard vampires and werewolves. You have to do your research into them in order to truly confront them. You can still have encounters with more typical monsters but the core idea is the important ones will have very individualized weaknesses, immunities and power (and ideally these are related to their backgrounds and the decisions that led them into darkness). Players who really want to end a dark lord as a threat, need to research their history, research prior encounters others have had with them, research monsters of their type etc. Even most of the general rules for such creatures are different in Ravenloft so a character like Conan coming from his world is going to have to adapt to the differences even when facing standard versions of the monsters.
Yes, D&D characters have a lot of power, especially at higher levels, so you are not playing John Harker (for that I suggest Masque of the Red Death

) but the system does a good job, at least in my opinion, of bringing gothic horror to the D&D experience. But there are also key changes, like alterations to existing spells (and IMO there is nothing stopping the GM from making further alterations to abilities or spells they feel upset the gothic atmosphere). Obviously if you want something that feels just like Dracula, a different setting and system is the way to go. But I have never had an issue getting players to investigate threats. You just have to lean into the advice in the boxed set and the rules unique to the setting around monsters.
There is going to be fighting for sure, but even Dracula ends in a large battle with the creature and his minions (that is how Quincey Morris bites it)
Another big part of what makes this stuff work, like I said, is running the villains as fleshed out characters who almost get into GMPC territory (this can be taken too far but done well it can work). The Black Boxed set calls out the sequence in Frakenstein where the creature tells Victor his story. The creature doesn't rip him limb from limb like he could. He has goals, he has a specific request and he wants Victor to understand his own culpability in everything that has transpired. This is in part to show how to make a sympathetic and thoughtful villain even if it has committed the ultimate act of murder. But it is also a demonstrating of how to run villains so that they are not just sitting there waiting to take swords in the face.
That said, it is a game. You can't control the players. If the players want to stab the creature in the face, they can try and there isn't anything you can do to make them play it more like Frankenstein. But I think there is enough reward for approaching monsters with more care, that it is pretty easy to do