I agree 100%. A company truly interested in fixing problems that cause turnover will already be paying attention to cues and clues. I've seen a lot of people go into an exit interview and sound off, all while justifying their ranting and complaining in their own heads: "I'm really just trying to help." That, of course, is bullshit.
Back in '98 (way early 20's) I worked as a Network Administrator. I was promised a promotion/raise but it kept getting delayed.
One day I got a call from a headhunter with a job/salary that matched what was promised me at my current company. I accepted the offer and left. In my exit interview, I explained how much I enjoyed the company (which was true) but it was time to take that next step. HR and my ex-boss were paying attention to the timing and undertones of my departure and did the simple math themselves.
Long story short, the new job didn't work out (I was put in charge of 14 doctors' offices and had no help). When my former boss heard, he offered me my job back, with the promised promotion. HR told me that my departure signaled to them that they had a bad habit of dragging their feet after indicating to someone they would be getting a promotion (I originally waited 3 months before I gave up). They changed their promote-from-within policies and practices as a result. Several years later when I was again promoted, I benefited from these new policies.
That company rehired me a second time about four years after that, and they contacted me again last year to see if I was available. They were willing to hire me a third time, even though I've quit several times. Why? Well, being a good employee helps... but so does shutting your face in the exit interview. Don't ever delude yourself into thinking you're helping anyone by "tactfully" outlining their problems.
Companies who are truly interested in fixing problems with turnover will figure things out for themselves. Your loyalty should be to yourself, and the best service you can do yourself when you quit is to STFU.