Your car, your problem. Either get someone to fess up, or take responsibility yourself and stop loaning it out.
There really is no difference between "who drove through a red light" and "who scratched the bumper while parking" here - how do you currently solve the latter one?
This is exactly how it works in plenty of countries, actually! The US is the outlier here. In practice people have zero trouble figuring out which family member was driving - just like they have no trouble getting a kid to fess up to scratching the bumper while backing up into their own garage.
The burden is on you to explain why the US should do things the way other countries do. What's better for everyone about that? Why should we change our notion of justice to make you feel better about it?
What proportion of road deaths are due to people running red lights versus just driving too fast for conditions, or being impaired at the wheel, or any number of things that these cameras don't enforce?
There really is no difference between "who drove through a red light" and "who scratched the bumper while parking" here - how do you currently solve the latter one?