Okay, so just about all the characters have done something dumb in the game, except Squall.

Quistis: Apologizing to Rinoa, will doing an important mission.
Going into the secret area in the training centre.
Rinoa: Do i need to start?
Irvine: almost didn't attempt to shoot the sorceress.
He is more focused in getting a Girlfriend.
Selphie: Just annoying. She probably makes one later in the game.
Zell: I Can not think of one, suprisingly. Only one i can think of is riding the T-board in garden.
Seifer: Went into restricted area in Dollet Mission.

Squall seems to be the only one focused on the missions and there importance.

Why couldn't the put other hardworking characters in the game?

Well, everything worked out nicely in the end, so obviously it was all meant to happen.

Isnt that the idea? A bunch of people who seem like they are unable to solve such problems, but overcome that at the end?

The game would be too boreing if all the characters were like Squall.