You are describing the current situation. But the genie is out of the bottle and you are not going to get it back in. At least, we can find some murderers. Consolation prize.
More power to ‘em for that.
Rapists too.
Real rapists. Assaults. Not the date rape that was really just a no-call-back.
Which brings up another question. Where does the line get drawn. Should one be drawn?
Forensic crime scene collection of DNA after petty larceny?
If the databases get big enough and efficient enough, I don’t see why not, as long as you can adequately prove no contamination or incidental evidence.
But again, the real danger isn’t catching criminals. That’s a pro that’s almost guaranteed to outweigh any imaginable con. The danger is when everyone’s data gets leaked to the private sector and the bad actors.