No, the fairness doctrine does not improve public discourse, because the fairness doctrine is no longer needed. With today's media, and the availability of the internet, information is available to anyone who wants it. There are so many different venues that people are able to find the information they want when they want it. There are viewpoints available to everyone. The doctrine is no longer relevant.
But it isn't. The FCC decided to eliminate the Doctrine in 1987, and in August 2011 the FCC formally removed the language that implemented the Doctrine. So, in reality, a doctrine that is no longer viable cannot improve anything. I think it was very good, it cleaned up a lot of the bias on the airwaves, but all in all, it's gone, so in the literal sense, no.