As 2D Castlevania flourished on the PS1 as it evolved into it's own type of search action genre with SotN, the N64 had what was supposed to be THE evolution of main Castlevania series into 3D, which unfortunately dropped the ball on it's first go and prematurely killed any momentum this franchise was meant to have with the 3D console games.
Castlevania 64 is not a BAD game per se, it's just a 3D take on Classicvania without any of the sauce that all the Castlevania is known for. Great music? Gone. Cool enemy designs? Gone. Satisfying combat? Gone. Challenging but fun platforming? Gone.
What you have is a very basic 3D game that feels like a student's first video game project. All of the elements of Castlevania are here, it's just all executed very basically resulting an a barebones boring video game that is not terrible, but not good either.
