1) Easy access to many high quality contents. For example HN is a good platform for accessing new knowledge. Note that I say "access", not "learn". Reading HN sometimes give people the false impression that they are learning new knowledge, which usually is not the case. I treat HN as a platform to get a peek at certain new knowledge, but reading books, watching videos and most importantly implementing it by myself, IMO, is the only true way to learn.
2) Fast enough to view high quality videos without any delay. Again this is related to learning new things. It is also important for me because it's one of the few ways that I entertain myself.
3) This might be arguable, but getting knowing a lot of different people from different places is a lot fun. People who comes from different culture usually have different standard of "good", "bad" and other moral judgment and it's fun to read all of those. This was doable 20 years ago but far fewer people were online at the time.
4) It's a lot cheaper. 20 years ago only a company can afford something faster than 1M (back then I had a 56K Modem I think but can't be sure) in my country and it was very expensive even for the modems. Nowadays pretty much everyone has access to some high speed internet. Even if they cannot afford a computer (which is actually a rare case), they have Internet access through mobile phones.