It gets cited in a lot of pop-science and podcasts, but it's not actually the groundbreaking, universally-accepted study that people think it is.
Likewise Gabor Mate is more of a podcast, pop-science guy, not a real researcher. Take his podcast and YouTube content with a grain of salt.
This reminds me, for example of the debate over Carl Jung. Some people say he set the field of psychology back with his scientifically untestable theories. Yet, I think it's obvious there is something to what he was saying, and it's likely he wasn't onto nonsense, but rather he was way ahead of his time.
So then why weren't addiction problems more widespread historically, like say 1900-1960? Life tended to have a lot more of what are generally considered traumatic experiences back then.
You just shrugged off opium dens, or moonshining, or whatever substances could be had. The demon liquor and marijuana and heroin were all well known.
But, people didn't care about the poor. Whether or not they do now, they do collect data about them. We don't necessarily have great understanding about prevalence of who used them how often, so we shouldn't pretend there was a significant difference unless there's a reason to. Nostalgia or rose-colored glasses or pretences of a better time aren't valid reasons to break from expectation.
I don't think these are mutually exclusive. Society wide problems cause a huge fraction of the population to experience severe emotional trauma, and the process of addiction largely seems to be an experience of trying to escape the feelings associated with that. If you can understand this process, you can take ownership of it, and have a path to beating the addiction itself.
Ultimately, there is a lot of disagreement about what addiction is and how it really works, but I think this emotional trauma aspect is a key part of explaining why one person can use a drug recreationally or for medical purposes without addiction, and another can't. It explains a lot of weird observations that just didn't make sense with the classical chemical/neutrotransmitter model of addiction.
These links I think help explain this better than I can:
How Childhood Trauma Leads to Addiction - Gabor Maté https://www.youtube.com/watch?v=BVg2bfqblGI
Comic explaining the Rat Park research on addiction https://www.stuartmcmillen.com/comic/rat-park/
These ideas have explained why I personally have never been able to fight addictions through willpower alone, but have been able to eliminate addiction with other techniques that seem unrelated- therapy, meditation, exercise, hobbies, friends, ending bad relationships, etc. It seems that while chemical/physical addiction is a thing, emotionally and mentally healthy people don't experience opioids as a positive thing, such that the effect of the drug itself actually discourages it's use, and even motivates the experience of withdrawal.