There are two kinds of people: people that do things(good or bad) and people that don't.
People that don't do anything love to criticize those that do. You will find them criticizing how bad other person dances in a party, but of course you won't find them dancing as is risky for them.
Well, yes, facebook sucks, but as the most important social network on earth, they suck less than the alternatives. If you have a better idea you are free to do something about it.