Not always, There are some game where leveling up does not significantly add to your party fighting ability, collecting, buying and timing are the way to go then. It's a way to replace the level up grind by another kind of levelup but it as a tendency of making the game more complex and it does tend to push you to your friendly strategy guide.
And then you have the all the monster level at the same time as you aka FF8, Oblivion so leveling is useless in this system as well.