NTR or not, why would a corruption-based game put a large focus on vanilla content? It's just not even remotely the point of it, the crumb of vanilla is there simply to make the female lead's corruption not inevitable and thus a bit more meaningful narratively when it does happen. That's its only purpose because neither the author nor their target audience care about the alternative. You're just not the target audience for these types of games and that's okay.
Say a game has an even split of vanilla/non-vanilla content. That would just mean everyone with a clear preference for one or the other would not care about 50% of the game's content, as opposed to a whole group of people enjoying the entirety of it and fully getting their money's worth out of the thing.