Some (not all) addiction is best characterized as a disease. The hold of the drugs is stronger than the will. Addiction can occur on a first use with some drugs, such as crack. The real problem is how to separate the true addicts from the wastrels.
Anything that involves free will and choice is not a disease. Drug addiction is not a disease, people choose whether to take drugs or not. Once addicted, they can choose to get treatment if necessary. It’s available. Calling every moral failing a disease is a moral failing in itself, removing personal responsiblity.
People can choose whether to take antibiotics - does that mean a bacterial infection is not a disease?