The DS games are far from terrible and they only sell like 100k units anyway.
I don't see why people think they're anything better than half assed efforts.
Basically you just throw together a large ass, complicated castle. Be sure to throw in some backtracking. If Iga is feeling especially adventurous, make two castles and some kind of city in between them. Palette swap enemies or barely modify them at best and you have the enemies. Basically all you have to do is copy Symphony of the Night but make enough minor changes to make it seem like a different game without fucking it up. Even then, sometimes they can't do that (Harmony of Dissonance)
Having played every single Metroidvania except for the second DS one, you can't be shocked at Castlevania Fighters Wii. It essentially follows the same half assed formula that made people cream their pants for the handheld CV games. Maybe if gamers stopped buying their mediocre offerings, this game would have never existed.
When did I say they were AAA high-budget efforts? I just said they barely sell at all lol
I don't see how triple dipping in some rehashes means that some lame waggle spinoff is an eventuality