I'm going to say that more specifically than the internet, the most important development was Wikipedia. Because the original internet was more or less an improved telephone, but the idea of putting all of humanity's collective knowledge on there is what makes it great.
For a personal example, I grew up out in the boonies where schooling is terrible. I learned SO MUCH from the internet, and wikipedia specifically. I know anyone can put anything on there, but if you're a rural kid who actually wants to learn a basic overview of scientific concepts/history, that is by far the best tool. I know I'm not the only one from that situation who is immensely thankful for the idea of putting knowledge online.