Well firstly when they say, where are all the nice guys etc, what they are actually saying is, a guy wont f*ck their best mate behind their back, they still want their "nice guy" to be a looker and they are hardly going to say, I am high maintenance stroppy bint who is mad as a cut snake, as I am sure you havent put the anything that might give a bad impression.
Even the plain janes will get bombared with messages, which in turn makes them believe they are better looking than they actually are, its a numbers game, you are just a number in the game.
Get some real thick skin dude, you will need it and thats before you actually get to "meeting" and "dates". If your a bit fragile, dating sites will not be for you , your confidence will take a massive kicking so be prepared.