imagine the line thinking for other things. I have no idea when rape was introduced as an official law in the UK, but surely no one would argue that women weren't raped before that date because it wasn't illegal.
No - but when the non consensual penetration took place it wasn't a crime. That doesn't mean you can't view it as abhorrent but it's not a crime.
Marital rape was only outlawed in the last 40 years. You can look back and think it was terrible and repugnant and abusive but it wasn't a crime.
A crime is something that is against the law. If the law does not in someway prohibit an act or omission then it isn't a crime.