Addiction is not a disease in the same sense that AIDS, cancer or pathological illnesses are disease. Addiction is a disease in the sense that GAD and PTSD are disease - that is the disease model employed in modern psychiatric medicine. Bacteriological disease are different and function differently according to a more classic disease model, germ theory (a concept pioneered by Louis Pasteur in the mid 19th century). Germ theory, a classic pathological disease model, understands disease very differently than the current disease model employed by modern psychiatry.
If you know anything about how fucked up the history or modern psychiatry is, you will understand how problematically the psychiatric disease model pathologies mental health conditions - conditions including behavioral disorders, such as substance use disorder (such as the condition commonly referred to as "addiction"), and the various mood disorders (such as the condition commonly referred to as "depression").
The disease model employed by psychiatric medicine has historically been (and counties to be) a strong force in dehumanizing, stigmatizing and demonizing those who struggle with mental illness. This is just as the earlier conception of the disease model, based on germ theory, pathologized conditions such as TB and blood communicable disease like syphilis.
If you are interested in learning more about the problematic history of how addiction has been treated by psychiatric medicine check out Thomas Szasz rather intense book, Ceremonial Chemistry. Check out Caroline Jean Acker's phenomenal treatise on "Addiction Research in the Classic Era of Narcotic Control" and the pathologizing of addiction and mental illness entitled, Creating the American Junkie.
