...Except doctors are very busy people who often rely necessarily on drugmaker-published literature to update their knowledge on those products and ailments. They don't generally have the ability to conduct their own research. Therefore, your assertion that all doctors 'knew' that these drugs were addictive is simply untrue.
Now, there is definitely a spectrum of responsibility/guilt that could be applied to all parties here. In some ways, the buck even stops with the patient: it's their decision what to put in their mouth and swallow, and no one was holding a gun to their head and forcing them to take the meds they were prescribed. But that of course is a very skewed view on the subject of addiction.
The crux of the issue is how society decides to assign blame. Collectively, we seem have a hard time dumping more responsibility on patients. Plenty of doctors have been fined, lost licenses, and gone to prison. Heck, my own childhood physician lost his license. But we also understand that many doctors who made mistakes deserve some leniency because they were tasked with helping people in pain.
But the drug companies...it's hard to imagine that they deserve even a shred of clemency. Their only job was to produce a product and represent it truthfully. Their failure mode was knowing, made them vast sums, and destroyed many lives.