To a point I do agree, however you have different formations. People who specialise in different styles of play for the same position and of that if you say had 10 players for same position then I would suspect that you could choose 7 or so with their play style to be affective against the team you are currently playing.
I don't entirely understand what you're saying. You might pick 7 people who's playing style can slot in as defenders and midfielders? The point being, you need defenders and midfielders. That's kinda my whole point in fact. You can't have 11 attackers and nothing else. You simply wont win. That's not because of bad game design, it's a bad strategy for the game.
This is the same as having 5 DPS and one tank. It's just a bad strategy to win a game. Not bad game design. That's not to say you can't do it. I've done it. We had some much damage and the team was generally good players, but it's not going to work very often.
It is like choosing to play deep, go wide, short pass, long pass etc.
Yes, but quite often one strategy is clearly a better way to go given what your opponent is doing. You can do others and you still might win, especially if you have good enough players, but one way might give you a better chance.
Now the ones that are not affective directly to the opposite player however offer something else which may make the other team switch things and then open up new plays and thus others become much more affective.
But sometimes the opposing teams set up can nulify even a very good player in his choice and he would need to chose something different. As has been said, sometimes a very good opponent might need a specific counter, to give your own team the best chance.
If a football team has an amazing midfielder, you might stick your own best player on him, man to man.
I don't actually know anything about Football, so I can't go into a lot of detail. American Football I could talk forever. If you go against an agile QB, you might use a LB as a spy. This can weaken other areas of your D, but would safe guard you against him destroying you scrambling all the time. I don't see how it is even close to bad game design. I see it as the reverse. Good game design that allows strategy to have an effect on the outcome.