Seems to me around the time that it was ended there were several other things going on.
The advent of cable news networks which gave a massive incentive to sensationalism and strong partisan ties as multiple players joined the space with a need to create a sustainable viewership.
Satellite feeds became common ensuring a single message instead of having a layer of abstraction in the form of a local or regional newscaster; instead of relaying facts, they can relay a highly opinionated version.
Local and independent news stations were being purchased and consolidated into national telecom companies with their own partisan editorial bends, a la Nexstar and Sinclair.
I have to believe that all of the above had a much greater influence on news discourse in the past few decades than the elimination of the fairness doctrine. Furthermore, if you give government the power to regulate anything; always expect the current party in power to use that regulation as a weapon. Can you imagine what our leaders would do given even more power to control and manipulate the media narrative? Ending this was a good decision.