A person is identically equal to whatever was created by the circumstances of the universe. It's hard to come up with a good way to say this. I just don't see any difference between holding someone "personally" responsible for their actions and holding the product of genetics and environment responsible. I think what you're more opposed to is a punitive justice system rather than a corrective one. Give people an environment that is likely to change them for the better for society rather than pointlessly punishing them. Punishment is a futile exercise in revenge unless it is also effectively corrective discipline. I think that is what our justice system (in the US) is supposed to do, but it utterly fails at it.
I think you're right. There is some merit to putting people who might pose a danger to society behind bars, but this only addresses half of the issue. I'd like to see a justice system that recognizes ways to help those people develop into functional human beings. From what little I know, Scandinavian countries already take this approach, to some extent; is it working, I wonder?