Recognizing that people and society is not perfect and not perfectible is the antithesis of Utopian. Desiring laws that are necessary to curb dangerous things is not Utopian by definition.
I see a statist logic in the line of reasoning. All vice gets to belong to the state to manage - dope, prostitutes, etc. It’s really just another way to undermine virtue and expand the state.
Recognizing that people and society is not perfect and not perfectible is the antithesis of Utopian. Desiring laws that are necessary to curb dangerous things is not Utopian by definition.
To criminalize is not to curb, but in fact to remove the ability to curb - as I said, "putting vice outside the realm of effective regulation." For example: widespread tainting of alcohol existed in the USA only when alcohol was criminalized; and since well before any state had legalized pot, teens have reported that they could get it more easily than beer or cigarettes ... which is to be expected since legal sellers card and illegal sellers don't.