I mean, you're sort of trading one thing for another, although I'm pretty sure nobody's going to deny that marijuana has significantly less detrimental effects than alcohol. The problem I had was that it was way, way too easy to get a hold of, I had a disposable income, so I ended up smoking like every day for about a year. Not the best sort of habit to develop, and it made me laze around quite a bit and not really explore other methods of having fun. It's only recently I've realized that I just became a lazy pothead and I needed to stop doing it so damn much.
Weed is great, but like alcohol, it's something you should do in moderation. Smoke like once a week at most, maybe. Look for the signs you're developing a dependency if it starts to creep up, and know how to take the steps to avoid falling down that rabbit hole.