Not necessarily. The 3e fighter really doesn't get anything unique (barring a few exclusive feats of limited value), and that's fine. Not only fine, but great. If all the other classes were done the same way the game would work a lot better.
A class doesn't have to have anything unique to that class; it can be seen as simply a package of abilities. A skill-based system would allow you to select any feats and skills you wanted, while the fighter class forces you to gain hit points, base attack, fort saves, and combat-related feats all at the same time. Flexibility is lost, while there may be a gain in ease of play for someone who doesn't want to have to select all those things individually. There's no reason why sneak attack (and every other class ability) couldn't be made into a feat or skill, and classes simply created as packages of thematically related feats and skills. In fact, a skeleton of that idea was presented in Uneathed Arcana, with all the core classes condensed to
three generic customizable versions.
That would be the "Next" evolution of D&D's class system to my way of thinking.