It is a generational thing, but IMO you've got the wrong root cause. Discussion of the dangers of drinking stems from people choosing not to drink, and people are choosing not to drink because they are attending the kinds of social gatherings that are lubricated by alcohol less.
As such, I'm hesitant to point to the decline in alcohol sales as a public health win. If people were drinking less simply because they were choosing to drink less, that's probably a public health win. If people are drinking less because their social lives have evaporated, that's probably really bad.