Musical identity is whatever the composer chooses it to be. If it's a compliation of different styles, then that's it's identity. You don't have to like it, just like I don't have to like the identity MS and Oscar chose for the LoS games.
Sure, it's an identity, and I won't deny that when done right it can work, but from my experience, it typically results in a weaker identity than sticking with a singular style. Notable exceptions to that rule tend to be zany, cartoony, or crossover games.
IMO, the reason Castlevania gets away with it more often than not is because usually when a track deviates from its game's stylistic baseline, it's a familiar track from a previous game. That way you're still thinking "Oh, this is Castlevania! I remember this song from *insert title here*
Personally, I'm to the belief that we aren't aware(innately) of how other routes of travel would fair and even after we've experienced ONE particular route, we might think that route is the best(even though we only think that because it's the only one we've experienced). Many feel Oscar's composition fits the LoS perfectly, while others don't. But, had things been differently, and a different style was applied, what would we be thinking? Now, that many have listed to Oscar's songs, they can sort of guess what it might be, but they'll never REALLY know. My sister, who was big into Backstreet Boys and N*SYNC at the time told me, "How could anybody like Duran Duran? They're so cheesy!". I told her, "If you were a teen back then, you'd probably like them too!". She said she wouldn't, but really, her perception was only molded by her experience to that point. Who knows what she would've been like if she was a teen in the 80s. Maybe she'd like Duran Duran, or maybe she'd be into Depeche Mode, who knows? That being said, though the past is the past, I tend to keep my mind open regarding these types of things. You don't really know until you know, and even then, there are thousands of other ways things could've gone down(and thousands of ways they still COULD in the future).
Well seeing that the primary argument is that Yamane/old-school style music should have been applied to LoS2, it's easy to make an educated guess on what the result would be by playing older soundtracks while playing LoS2. From what Araujo has said, it's not like they sat down, looked at each other, and went "Ok, no experimentation, we're going with a completely new style of soundtrack". They experimented with it, and made a decision.
Sure, you can never be 100% certain, but life isn't about being 100% certain. "But it could have been better!" Maybe it could have been, or maybe it could have been worse.