Looking at the past Castlevania games, to them the past Castlevanias hold no water compared to the great things Castlevania HD offers for that audience, and not simply the multiplayer, that's just one part of the greater whole.
Please understand that Castlevania HD is the "dream game" for Castlevania fans and cooperative fans that like its style, you may scoff at that, but your rejection of this is no different than someone's rejection of World Cup soccer:
Those fans who think 'vania HD holds "water" (rotten water?) than the actual games it's stealing assets from is somewhat hilarious. That's like saying Mario games by Nintendo hold no water to the stuff people could make for Newgrounds...
And NO, HD is
not not not not not NOT the dream game Castlevania fans would like, and it's an awful multiplayer experience. I could go out of my way to create a much more rewarding and worthwhile multiplayer experience by mentioning a few points.
1: Give the game a narrative, and if you can't hammer a heavy narrative to the player, make the mode a side element to a single player campaign.
2: Give the player freedom in making a character. Don't stick them with popular characters from the series who have so many strange deviations from the actual games they're from that they come off as clunky.
3: Do more than steal assets ranging all the way back to 1986 and randomzing stage locations.
Harmony of Despair isn't a dream game for Castlevania fans, as it's more of a shining beacon of what people were getting tired with when it came to newer games; laziness and assets being reused. I mean come on...
Judgment has more new material for it than HD does. I don't see how you can argue that.