This is not exactly correct. When the book was written, a lot of commentators had written off television as useless garbage -- totally bad for society. Postman (correctly) complicates that by pointing out that television is great for emotional storytelling, and he is in favor of fictional television shows that model social values for people. Television turns everything into emotional content, which is why TV news evolved to be so sensationalistic -- TV is not good at news. Printed media is good at news. So, each media has uses that play to its strengths and weaknesses. When a medium is used in weak ways, that is bad for society.
(I don't know what the redeeming argument for TikTok would be...)