The charge is that he was a 30-plus year old man getting frisky with pants dropped with a 14-year old girl. Fourteen. Not "late teens and twenties".
And this accusation is all on the say-so of a woman who admits to going full blown loon at this time in her life. Her subsequent life's history also demonstrates she was a flake. I have seen claims that this woman has made this accusation against three other people, so how much credibility should we give this?
She has already been caught in a mistake (or lie) by claiming that her life went into the toilet after she claims to have met Moore, but when she was in court in 1979, she was in court precisely because her life had already turned into a mess. Drugs, promiscuity, suicide attempt, later multiple divorces, supposed multiple accusations against other men. What are we to make of her credibility?
You believe her because you
want to believe her. If this were a murder trial, most reasonable people would say "there is no way we can trust this woman's credibility because of her past behavior."
Coming forth after 38 years with this allegation is just another testament to her being a flake. If this was worthy of adjudication, the time was 38 years ago, not now.