So then why isn't Facebook as notable as laying the first landlines across the US? Sure it's not the first time people have been communicating in this way, but by your argument Facebook is implementing the way that the current generation communicates with each other. Now there certainly are nuances to the situation; there are parts about communicating through Facebook that are richer [1] and also scarier [2] than the telephone. But if your claim is that Facebook has taken place of the telephone for certain types of communication, I fail to see how that isn't changing the world.
[1] Sending various forms of media to each other, having a historical record of communication, etc.
[2] Privacy controls, control over your data, etc.