Your oldest is wise and is showing you he has made an effort to understand how alcoholism
In a parent affects children.

He is right, it’s familiar to you so you unknowingly learned how to become codependent from an early age.

You cannot fix an alcoholic. They have to make the decision to get sober and learn how to live a more functional life which includes becoming much more self aware. Self aware in recognizing how their behaviors and choices affect others.

Alcoholics make bad choices and like to play the victim and see others as the bad guy. They can be very moody and can hide their need for alcohol. They can seem friendly and warm and ok, yet that typically means they have alcohol in their system.