I'll admit, I've never been a fan of large structures, more so at night, so I'd be pretty scared of Castlevania even if it DIDN'T have monsters and like.
I don't think I'd really want to come across asshole skeletons tossing bones at my face, Medusa heads constantly trying to knock me into rusty/bloody/any spikes or bottomless pits-o-doom, merman shooting water in my freaking face and trying to knock me in to water to possibly drown me, bats--ugh, the BATS, the clocktower as a whole (I could just imagine me getting crushed between gears...), then there's the questionable meat hidden in the walls--who knows HOW old that crap is, candlesticks that erupt into hearts, which is a lot grosser upon reflection and I wouldn't even want to touch them, let alone use them to power questionable sub-weapons (what kind of weapons needs hearts to power them? Very questionable and possibly evil to me--where did those hearts even come from?! The innocent or warriors that failed before me?). I also wouldn't want to see the living embodiment of Death, let alone have to fight him and have to deal with his Kung-Fu tendencies.
Then there's Dracula...and all his bull crap. I'd have to sit through his boring monologue speeches about hating humans and god, and calling me out of my name and throwing blood filled glasses at me. And then there's the fireballs, the transformations, the blood rain...*sighs*