No on both counts.
Most drugs are social, like pot, LSD, THC, etc.
Our society has strong social inhibitions and stress, and drugs help people relax back down to more normal.
And no, alcohol use was higher when illegal because there were more people pushing it, and there was a fairly universal resentment against those who made it illegal.
And it is absolutely FALSE that the legislators get to arbitrarily decide what is legal or not.
As a democratic republic, the legislators are ONLY supposed to be able to defend the inherent rights of individuals.
So then legislators could only make drugs illegal if they cause the rights of others to be violated, which is NOT the case.
So criminalizing drugs is inherently totalitarian and illegal.
As for black market, I do not have CO experience, but almost all states are in the process of legalization.
It appears to be working fine to everyone else.