Blocking new players from harder heroes isn't going to do anything but piss them off. The only way to learn is to play. All the game needs is some sort of way upon open beta or release to inform new players what heroes are recommended for beginners. They take the advice or not. You're not going to learn by just steadily unlocking other heroes. You're going to learn by losing. A lot. Until you figure out just what you should be doing. I don't learn jack shit when I win a game. I learn what I need to improve or what I did wrong when I lose one.