I think it's both admirable and naive. My experience with upper management is that it rots from the top, so if you're quitting due to systemic issues or because of your boss, it's very likely due in part to upper management's inability to listen before something blows up.
In game theory terms it's pretty much all downside. If you say nothing or if management sends exit interviews straight to the recycle bin, there is zero payoff for you and zero payoff for anyone else. If you say something and management is bad at listening, you burn bridges and nobody else benefits. If you say something and management is good, you get nothing and others after you benefit. More often than not management is bad at listening. In other words, it never improves anything for you and rarely improves anything for others.
I used to be a strong believer in giving honest feedback during exit interviews, but I definitely don't anymore. If upper management actually cared, they would have gotten and acted on the same feedback from current employees, before they quit. I no longer believe in offering crappy management the privilege of a "I quit" wake-up call at the risk of my own professional reputation/relationships.