Yeah, it was circumscribed, all right. Section 2 took the "wet/dry" decision from the federal government and gave it exclusively to the states.
You want to do that with drugs, fine. Pass an amendment similar the 21st, Section 2, and you got it.
Section 2 of the 21st amendment demonstrates that the federal government had the power to prohibit alcohol. If they didn't, only Section 1 of the 21st amendment would have been necessary.
If your silly reading were correct, Section 2 would have been redundant, and thus left out.