(SEE EDIT below for demo thoughts.) Haven't played it, but I think they've done something smart based on the gameplay I've seen. Visually and mechanically, it satisfies the broad modern Metroidvania audience expectations, even if it might seem a little too far to longtime Castlevania fans. Yet within the mechanics it still is clearly referencing the whole of Castlevania, including some very deep cuts from GB Legends and Circle of the Moon. It also was sure to have a lot of the iconic enemies and bosses. And even within the over-the-top, flashy visuals, it still has some art references/motifs to Castlevania writ large. Those things ensure it doesn't separate it from core Castlevania. And by having action but an emphasis on platforming, and making exploration the format, it hits both Classicvania and Metroidvania wants. Back to the visuals, they bring in the Netflix Castlevania fans who may have avoided most or all of the games. So, it may not 100% satisfy every one of these audiences, but I think it ensures interest and sales from a wide swathe of audiences and makes Castlevania more relevant for newcomers.
My opinion is the art direction is not ideal, but it's not horrible. And the gameplay looks like a very interesting mix that respects the entirety of the series. My hype is about a 6 or 7 out of 10, but I think as a whole game experience, it'll be an 8.5 or 9 out of 10.
EDIT: Completed Demo and did some of the extra content in it. Demo progress save data carries to main game, it says. We're back, people! This is 100% Castlevania for this generation. It's got a little bit of everything and it comes out great. The gameplay with the whip is a dream come true. I'd say what you've got here design-wise is Circle of the Moon meets Silksong meets Blasphemous. That said, it still feels like its own thing--a distinct experience where people can really get into the series. It really honors the Classicvania while also having Metroidvania, too. The art direction is really good, but the art style will be a bit divisive. I wouldn't want this art style for all future Castlevania, but for this one, it works fine and looks good in person. The music is serviceable. Not overwhelming or something you'd want to listen to a ton outside the game so far, but fitting in context. The challenge level is raised right from the start, more along the lines of Blasphemous...maybe a little easier than that, though. But it has more of that Classicvania learning curve, which I love. There are spike traps and such, too. I'm not sure how the Church is being handled so far...there are slight hints of Netflix there. But the "mystery" aspect of it has a Migami flavor from Chronicles of the Wolf and The Lecarde Chronicles 1 and 2. Anyway, demo took care of doubts I have. Feels like a 9 out of 10 right now.
For reference, my favorite Classicvanias are Castlevania III, Lecarde Chronicles 1, Super Castlevania IV, Dracula X SNES, Bloodlines. My favorite Metroidvanias are The Lecarde Chronicles 2, Circle of the Moon, Simon's Quest, and Symphony of the Night. My favorite 3Dvanias are Castlevania 64 and Lament of Innocence.