The value on the bullpen is completely different then it was when Mariano entered the game.
Don't even know how that's debatable and a major reason for it is because of his dominance.
As everyone has said to you already, the evolution of the bullpen began before Mariano Rivera. You're making it sound as if the modern bullpen developed as a result of Rivera. In fact, I think the opposite is true: Rivera was allowed to become as dominant as he was because the modern closer position had already been established when he arrived.
You're entitled to your opinion, for sure. But the idea that modern bullpens are structured as they are because of him is just factually incorrect.