The "IGA route" is the "Konami route". IGA just works/worked for them.
It is almost a weird science how IGA gets shoehorned into whenever anything about the quality or the future of Castlevania is mentioned. He isn't left alone even after apparently no longer working on Castlevania. What does it take for him to be not excluded as the bringer of all things that spell Castlevania's ruin? Would getting crucified help?
If Mercurysteam calls it quits after this, you could say they were "noble" or "smart". But they would also get off easy by getting out while the going's good. Their games were compared to repetitive gameplay implementation, zany, kind-of-insulting side projects and the increasing marginalization of Castlevania. I don't know what exactly went on in Konami over those years when they didn't bother investing on Castlevania, but lots of things in LoS can't help but look better in comparison to those. It can be partly like some sort of tunnel vision effect. It sort of links into IGA; he had the misfortune/fortune of producing so many games that it was inevitable some of the praise would turn into hate. Had he produced only a trilogy, how would things be now?
But if they stick around longer, will the novelty of those things keep on shining as bright? They don't necessarily need to innovate anything if they jump out of the ship and the producer doesn't have to become Mr. Castlevania. Just doing three games that aren't like the Vanias whose aftertaste some of us, lots of us, have been wanting to get out of our mouth would be enough.