The law is a very blunt instrument and engagement in sexual relations is typically a relatively nuanced and protracted series of actions.

Much of what ends up in the criminal law sphere might be characterized as 'sex by misadventure' where two people have each behaved badly and found themselves taking actions that later produce shame and hurt.  Other instances, such as the two cases cited, involve what appears to be appalling behaviour inflicted by someone in a position of trust upon another who is incapacitated, but the actions taken cannot be substantiated sufficiently to satisfy the proof beyond a reasonable doubt test needed to assign criminal responsibility.

Maybe what we need as a society is a form of civil citation involving outcomes like community service and remedial education, and a standard of proof that is less onerous than the criminal responsibility test?  Reducing the stakes and increasing awareness could produce better outcomes in these grey areas where the law fails.