The difference is alcohol was legal to begin with. Crack and fentanyl never were as far as I know.Some of the problems are discussed here
Unintended Consequences | Prohibition | Ken Burns | PBS
The story of the rise, rule, and fall of prohibition and the entire era it encompassed. Full film now streaming.www.pbs.org
And actual statistics here
POV: The 100th Anniversary of Prohibition Reminds Us That Bans Rarely Work
Ultimately, it did not result in a significant or lasting drop in alcohol consumption, argues Questrom School of Business lecturer Jay Zagorsky.www.bu.edu
Initially alcohol use dropped drastically once prohibition was enacted, but after a couple years once organized crime got hold it was back over 70% of the level from when it was legal.
While it dropped for some demographics, it actually increased for others.
And obviously respect for the rule law went right out the window for the majority of the country.
Turns out having laws that people think are bad makes people lose respect for the law in general. The damage that does to a society cannot be overstated.