No, it's kind of like saying that people should only be convicted in a court of law when the prosecution shows all available and relevant evidence to convince a jury of their guilt, and if convicted the punishment should fit the crime.
Again, you're suggesting that criminals shouldn't face punishment because it's society's fault that the crime wasn't deterred in the first place.
What I'm saying is that the percentage of criminals who are actually punished has very little practical effect. It doesn't affect deterrence because the other prospective criminals never know about it either way. It won't make any particular criminal's victims whole either way (if anything it makes it worse by reducing their ability to pay restitution). It doesn't reduce recidivism.
It's not that we shouldn't try to do it. It's that failure is mostly irrelevant.
Again, you're suggesting that criminals shouldn't face punishment because it's society's fault that the crime wasn't deterred in the first place.