So, are the eschewing the 3D because they want to make a real game? What? The 3DS has TONS of great games that utilize this unique feature. Is it possible the parallax backgrounds described are in 3D, if one so chose?
I can't tell you how restrained I've felt while playing Castlevania. The backdrops are so GORGEOUS, and often you go by open doorways or cavern entrances or wispy, dust-blown roads. They're all very enticing to look at, but alas, you're forced down your fixed 2.5D path. Sweet agony!