Honestly? I'm willing to bet he just got lucky with OoE. The right combination of a GOOD visual style, and a NON-INTRUSIVE gimmick, which makes the weapons gameplay similar to the SoTN format of different weapons. And an alright story because there was a large gap that there was no issue tossing something in there, which happened to make sense. It's not that IGA can't make good Castlevania games, it's just that A) he sucks at sequels, B) his gimmick driven development process, (gimmick first, story later) tends to bite his games in the ass, and C) his constant reuse of SC4, Rondo and SoTN Assets gets old real fast. (directly ripping the save room from SoTN for HoD is completely unforgivable)
(apart from Time Reaper, but atleast they didn't do copypasta like in the other games)
Still ridiculously lazy. And completely strange and out of place, too, considering up till that point, everything else is original, from scratch, yet for some reason, it's like they got to the Time reaper, and IGA just suddenly got a compulsive need to reuse an asset.
But you know, those aren't even the reasons I don't want him back. (Though they factor in)
It's that he has had his run, and we don't need more of the same. It's time to move on from the IGA era, and get different people involved. Different points of view, different ideas, different visions.