Going soft on that is as stupid as embracing socialism.
I think the difference is similar to the way Prohibition was handled. As far as I can tell, in the ultimately unsuccessful attempt to enforce Prohibition, those who trafficked in alcohol were prosecuted, but those who drank the alcohol were not. If we were to do the same today, trafficking in drugs would be a crime but possessing and using the drugs, though also presently illegal, would not be prosecuted. Unless and until any drugs presently illegal become legal, that would be a big step towards prison reform.
And one more thing: the anti-marijuana train went off the tracks a long time ago; that is a battle we cannot win with LEOs and in the courts.
Full disclosure: I'm mid 60s, never been drunk, rarely have alcohol outside of communion (the last time was I think two years ago), and I have never touched marijuana nor taken any controlled substance--in short, I don't have a dog in the hunt.