Actually, if you have people playing that understand the game, you can shut MANY champs down, even if they have a great early game.
If Katarina shows up, take someone who has a silence, such as Cho'gath or Garen. They can withstand her attacks and silence her.
Yasuo has great early game but is very squishy. Snares can stop him in his tracks and make him useless while your team gangs up on him and kills him.
Fiora, does not do well against tanks. She is very AA reliant. Build a Thornmail and more tank items and she can't kill you as easily.
Blitz, he is pretty useless in my opinion anyways unless he can land a grab. If you position yourself to not be grabbed, he cannot do anything besides run around.
It's all about knowing how to shut down these champs in the first place. If you watch HIGH elo games, most of the champions you even named are rarely banned. It's all about knowledge and planning your team. Half the reason why i don't play Blind Pick modes(Norm Blind Pick and Team Builder). Not to mention i can't stand the instant spot spamming and then people dodging because they don't get what they want.
Hope this helps you out a little bit. Believe me, if you keep an open mind and plan for the match up's, this game becomes a lot easier for yourself. Granted your teammates do that same(which isn't always the case), but you get what i mean.