I feel like it's likely a larger proportion of weed-users have it affect their productivity and motivation to grow in life than the proportion of drinkers who become dangerous alcoholics or end up with cirrhosis. I don't have data to back this up though.

I've seen more lives around me hampered by marijuana than by alcohol, despite having a very large amount of heavy drinkers in my circles.

I agree and I've seen the same.

However as far as actual physical health (rather then mental or social) I believe cannabis to be far less detrimental.

It might demotivate a person but it doesn't flat out kill them.

Is it also possible that alcohol is the lubricant for a society with dysfunctional social and environmental principles? Perhaps what we sometimes describe as motivation or personal growth isn’t actually that valuable when directed at goals that destroy the planet and isolate us from other humans.

Don't have any facts to back the assumption up, but I'd agree that alcohol is harder on the body.

Apart from the effects on the brain, there is also the weight issue when drinking both beer and wine.

It's amazing to me how much difference just 6-7 kg less weight makes.