I think the point of several of the 'boring' Starks is to play the roles of the traditional 'good guys' to reflect how silly, ineffective, and downright uninteresting those sorts of characters are in as un fairy-tale like world as the ASoIF universe. Ned was the good and honest man who always tried to do the 'right' thing by the standards of traditional fantasy. Robb is the young hero who is driven to take up arms in righteous rebellion against the powerful and evil foe that has wronged him. Sansa is the princess who sits in a tower and waits for Prince Charming to come and rescue her because she can't do anything for herself. Catelyn is the myopic mother who is so focused on the immediate safety of her family that she can't make sound strategic judgements that account for the world at large.
While I find their motivations and lack of efficacy rather dull I think it's interesting having them around as something of a 'good/neutral' party on the morality scale to reflect how much more successful and effective the schemers and plotters are at achieving their goals than the upstanding and morally courageous types who can't seem to get much for all their righteousness and senses of propriety. I also find it interesting that all of the Starks who seem to fail so miserably are the heads/first-borns of the Stark line. While the the illegitimate/second children, have gone in a rather different direction and have amply demonstrated a superior ability to roll with the punches the world keeps throwing at them and keep going strong.