It's actually quite an interesting subject. It is an alternative, but it isn't without it's own issues.
There used to be commercials that would show a guy smoking weed and his mother would say. Did you find a job yet, and he would say not yet. (because he was smoking weed) and then it said, weed will make you do nothing too. That is exactly what it does.
So, while it's less harmful to the body that alcohol. It can be harmful to your well being because you become so lethargic you don't do anything. Including work.
In the end, at least weed isn't addictive like alcohol to the point that the withdraws symptoms alone can kill you. Though, you can't let it rule your life either.
If necessary, it's better to ween off alcohol onto weed then use a busy life to help ween you off marijuana I suppose. It's a safer way to exit.