Items make the game unbalanced by most players' competitive standards. That is all you need to know.
In the competitive scene, most people view using items against an opponent as showing less about your own skill because the items themselves are extremely powerful and are awarded to you at random conditions in the game (further making the game less about using one's own skill to overcome the opponent).
What do most people find as the solution? Turning items off and it avoiding the problem entirely.