I don't see why the police are getting it in the neck for this.
Down the years many sets of circumstances have fallen one side or the other of the borderline as to what is criminal and what is civil.
Remember also that the police no longer have the responsibility to prosecute criminal offences - it's the job of the Crown Prosecution Service to decide whether a person should be charged with a criminal offence, and if so, what that offence should be.
Clearly, if the evidence suggested no criminal offence had been committed then there could be only one outcome.
Just because many of us might think that the criminal law has been breached in any given set of circumstances doesn't mean it has been and, in any case, most of us are not legally trained and rarely if ever are privy to all the facts surrounding an investigation.
If anyone is to blame for the sometimes blurred position of the criminal law vis-a-vis the civil law it's the law makers, ie Parliament.