I'd hate to get all true scotsman but a true leftist would never preach for prohibition as a solution for vice.
But the audience for these anti-vice takes seems to be "lefty" people. Both center-left folks and also leftists. I see plenty of folks on Bluesky who want a socialist revolution tomorrow that also want to ban gambling.
That's what happens when you squash a multi-dimensional space of political beliefs down into a single dimension of left-right. You can't have a meaningful discussion about anything from this starting point.
Viewed from a 2-dimensional spectrum this problem lies on the social authoritarian-libertarian axis, not the economic left-right axis.
I'd consider myself a "true leftist" and while I don't think prohibition usually works, I also don't believe in absolutes of liberalism where everything goes - where corner shops can sell heroin and if you fall into addiction that's just your own moral failing.
I support individuals' freedom to use drugs in a controlled, responsible manner, but there need to be limits somewhere to protect naive individuals from getting themselves into something they'll regret and to protect society from collapsing.
The case of US Democrats is an example of how useless the 1-dimensional classification is. They can be very socially progressive which would seem to put them well into the "left-wing" territory, but economically they're in the right-wing territory.
Economically speaking, a candidate like Sanders (considered to be too radical even by the Democrats and painted as an extremist by the Republicans) would be considered centrist/centre-left in most of Europe. He supports single payer healthcare and policies that would strengthen worker protections and improve the social safety net, but he doesn't fundamentally oppose capitalism. That's the status quo in most of Europe.
There are some EU laws that are more conservative and some that are less, proponents of policies often cherry-pick the ones that match their ideology leaving out others. Even worse is they ignore the problems that the policies they agree with are causing those countries, but ends-justify-means.