Not only are is the Drug war a fundamental breach of individuals' freedom, there is nearly no evidence that it has actually worked. If there was tangible evidence and data to suggest that the drug war was lowering drug usage, supply, and drug overdoses, then a rational argument could be made for the continuation of the drug war.
Even if this evidence was present it is still a massive intrusion into individuals freedom, but the fact that the drug war has been an absolute failure should validate the need for a new strategy. The opiate epidemic is truly an awful thing, but the government trying to enforce their way out of the opiate crisis is a completely ineffective method in the long term.
If there is a demand for a good, then the supply will follow, specifically in regards to black market goods because of the increased profit margins sellers receive compared to traditional products. The current structuring of laws sends many offenders to prison for much longer sentences than needed, which has consequences throughout the country, but specifically in low-income areas.
The government could never obtain the amount of resources needed to successfully achieve the goal of the drug war through enforcement. You mentioned the old TV ads of this is your brain on drugs, and I think that the governments continuation of their "propaganda" makes individuals question all information that the government is telling them about drugs. If the government tells teenagers exaggerated and untrue facts about marijuana, when those teens get older and realise that much of what they learned was simply not true, then are more likely to disregard all of the drug education they received through public school or government information.
An individual's feelings regarding drug use should be largely irrelevant to their beliefs on it. Even if an individual believes all drugs are dangerous and discourages their use, the continuation of the war on drugs is not a viable method for stopping drug use.

I think one of the most effective ways to reduce drug use is to simply present honest information. Instead of saying that marijuana will give you this or that type of cancer, I believe information should be presented in a manner such as, "You may never well enjoy marijuana, but these are the consequences and effects it can have on your life.". Individuals who are interested in drugs already know that they may like them, because so many people do. This wouldn't be promotion of condoning drug use, but simply an objective and honest look at drug use that individuals would likely be much more receptive to.