The idea of "powerlessness" can be thought of with the same nuances, I think. Thinking you are "powerless" over an addictive substance in an absolute sense is dangerous and irrational. But, addiction, by definition, means that you have an involuntary relationship with something. So, you are "powerless" to some extent.
What you say makes a lot of sense. That being said, nothing that makes sense treats the ISM component of alcohol-ISM. The concept of "powerless" appears to be dangerous from the perspective of Philosophical Rationalism. Keep in mind that there were philosophers who never bought into Rationalism (such as Kierkegaard and Heraclitus).
Powerless is used to describe more than just managing alcohol. It is also related to the "- that our lives had become unmanageable" part as well. By admitting we are powerless, we are allowing a alternative source of power into our lives.
If that does not make sense, keep in mind that Spiritual Principles don't need to make sense to get results. If you are willing to do some serious homework on this concept, read up on "Wu Wei" of Taoism.
Wu wei - Wikipedia, the free encyclopedia