They're saying there's nothing effective we can do.
There is something effective we can do. I'm not saying "people can still get drugs even though they're illegal, therefore we should legalize drugs", because that doesn't make sense. People still commit murder, but that doesn't mean we should legalize that. What I'm saying is that if we want to stop people from using drugs, it's been proven that there are better ways to do that than sending people to jail for using them. And also that people don't deserve to go to jail for smoking a joint, or even shooting heroin.
If you reduce the supply of something (by banning it and enforcing that ban), it will become more expensive and fewer people will be able to use it. You're not necessarily going to end all use of illegal drugs, but you will reduce their use.
If you're saying the drug market isn't like a regular market, you're going to have to explain why.
I don't deny that banning drugs makes them more
expensive, what I'm saying is that the evidence (see the link I already provided) shows that drug use decreases when it's approached as a medical rather than criminal problem. Also, the effects of criminalization, e.g. organized crime, are unacceptable. Even if decriminalization raised drug use, which the evidence shows that it doesn't, I would still support legalization, for the simple fact that we'd no longer have people killing each other over drugs.