One of the most misunderstood things that Marshall McLuhan has ever said. He was very specific about what he meant by "media". In essence, he meant "any technology or development that acts as a tool, extending human capability". Also, he was very specific: by "message" he meant "repercussions/advances changes in society produced by this tool".
The core problem that many have with this statement. is that people already understand "media" to mean "vessel to communicate", e.g. radio, television, writing, movies - and "message" as "content".
The short version of what he was actually saying was that people get far too hung up on the content and/or purpose of a technology, without realizing what it will actually do. His example was that the electric light bulb (medium) allowed for complex eye surgery or open heart surgery that would have been impossible given the contamination of a sooty burning piece of wood being used as illumination. Or that a gas lamp could ignite bowel gases, making abdominal surgery really risky. The steam shovel put a lot of ditch diggers out of work. Combine harvesters also meant most of the population no longer had to work on farms.
Every time a new medium comes along, the people who developed it always came to the table with the idea that it would enlighten and enrich and uplift the human race. With the advent of television, why, people could attend open university lectures and watch plays and listen to classic Greek poetry! Not realizing that what it would actually be used for would be mindless television comedies and reality shows. We could have had virtual reality in the 1990s, but its inventor, Jarod Lanier, refused to allow it to be used for pornography and/or military applications - which are the two main drivers for the development of most new technologies. The VCR was used in its inception to allow people to keep their own porn on hand rather than being seen going into a seedy theater.
Take the World Wide Web, which was originally designed to share hyperlinked documents - the idea being that the free and open sharing of information would allow humans to get smarter, to build communities, and shrink the physical and cultural differences between peoples. Well, some of that does take place, sure. But what we've ended up with more often than not are memes, echo chambers and if anything a shrinking of people's circle of friends.
Noted cultural satire South Park put it very elegantly in its song, "Safe Space" -
"If you do not like me
You are not allowed
In my safe space (my safe space)
Look and you will see
There's a very select crowd
In your safe space (my safe space)
People that support me
Mixed in with
More people that support me
And say nice things"
If anything, we've ended up with a general lack of empathy and/or any real paricipation - instead flocking to hugboxes that cater to own specific sense of self.
The promise was that the global village would shrink in size - and people could form friendships with people anywhere, regardless of distance. Unfortunately, for far too many it has done the complete opposite - having people segregate very vigorously by point of view, with no quarter or compromise with any other worldview - preferring the company of a like minded fellow halfway across the world than the actual, very real human being next door.
In addition, it's put an enormous number of people out of work, and almost completely enslaved a minority of those still considered useful. Travel agencies are all but dead in an age of Expedia. Amazon has put most bookstores out of commission, those that weren't destroyed already by WalMart selling the latest hit book as a loss leader. People now demand that these sites run 24 hours a day, meaning that many tech folks are literally 24/7 on call.
When robotics come in en masse, and we're seeing this now with fast food workers being replaced by self-serve kiosks and robots, checkout cashiers replaced with automated kiosks and bank tellers replaced by machines - how will most people be able to justify their experience? Farm workers can be trained to operate machines, but not everybody can be a highly educated savant doing research or engineering on a nanotechnology level. In theory most people could live a pretty good existence on a guaranteed income, being paid to produce content and experiences. Time will tell how that actually pans out. I'm not hopeful though, especially since most people are looking at each other with disdain.