I'd be sad if this were a Castlevania game; I'm sure I'd be much less forgiving of its not-so-great parts if it were one.
I gotta say, though, I do dig the level designs. They're a bit wonky, but are also a bit more fun and varied than what you'd find in most Metroidvanias. A lot of it wouldn't work for a Castlevania game—turning into a fish, beetle, or water elemental would be strange in a CV game, and many of the level structures are based on these abilities—but it's really cool for what it is, and I wish Konami would take a couple notes and realize that they seriously need to start designing areas that are fun, intriguing, and not copy-paste and bland. (I'm sick of huge corridors with no interesting ledges or platforms. Really, really sick of them.)