I think they were more substantive when they were less visual. TV made communication more superficial. That's why those who listened to the first Nixon-Kennedy debate thought Nixon won, but those who watched it on TV saw Nixon's shadowy makeup and thought he lost.

https://www.thestar.com/opinion/contributors/think-donald-trump-won-the-debate-read-the-transcript/article_af49e542-3888-11ef-a5eb-c71f4e7dfc70.html