Is it really "plain and simple"? The nuance I'm asking for is if neither person consents under our definition of consent, as well as how to tell whether a "perpetrator" actually exists.

For example, in this other thread there is argument over whether all prostitution is rape - even when the sex worker went into the business voluntarily and is not trafficked. My point is that using your definition, it's not always possible to tell if a rape actually occurred, because consent isn't just "you either consent or you can't consent".