Edit: I'm not saying the medium has zero influence on the message. I'm just pointing out that a) the medium does not dictate the message, and b) effectively "beauty is in the eye of the beholder".
McLuhan's point of view was that the means for media delivery have a much more significant global impact than the content contained within the media itself.
He did not contend that the content was meaningless, or lacked a message. He did, however, quip throughout his life that focusing on the content is putting the cart before the horse.
Communication theory is the medium constrains the possible messages. Further, McLuhan, Postman, others are saying various mediums have their own intrinsic dominate properties, character, which crowd out most other messages. TV gave us the sound bite. Usenet gave us trolls. Twitter gave us Trump. Facebook gave us "fake news" (aka gossip posing as truth).
The medium is the message.