Castlevania > Demon Slayer (Kimetsu No Yaiba)
The only mildly warm part of this take is that Castlevania isn't really anime but western animation.
Demon Slayer has amazing visuals thanks to Ufotable, but outside of that the story and characters are as bland as, if not even worse than in any other painfully mediocre battle shonen to ever come out. If you look at shows as a whole instead of hyper-focusing on animation quality, pretty much anything with even mediocre writing will beat it.