Ill bet if it was set in Eastern Europe, and had the exact same elements, (Set in Romania instead of japan, the church seals it away instead of a Shinto priest, Soma and Mina are European instead of Japanese, etc etc.) you wouldn't be complaining.
I probably would, because Castlevania should not be an anime.
Up until Aria, you had maybe a few Japanese weapons show up, and a few suits of armor, but that's hardly a connection to be made.
Suddenly, HEY WHOA WE'RE SET IN JAPAN NOW! And it stars a Japanese high school student who is the reincarnation/descendant of the Devil King/Dracula! And his girlfriend's family is implied to have sealed said Devil King/Dracula! And Alucard has become "mysterious man in a suit"! Also, you have Julius, the "grizzled old mentor" character, Yoko, the "wise priest" archetype, Hammer, the "lovable softie", and Graham, the "Affably Evil" antagonist.
Yep. TOTALLY NOT AN ANIME.
*cue earlier points from this side of argument*