"The Web" and "E-Commerce" ended up being quite gigantic "unmet niches" though!
If you're defining "successful" in the sense of people-making-a-lot-of-money I completely agree.
If you're talking about the internet in 2005 vs 2025, smartphones completely ruined the internet. At one point I had half my high school using HTML in their AIM profiles because they thought mine was cool.
Now kids can hardly even type on an actual, physical keyboard.
I'd argue that's because the tech wasn't there yet. Not the network or other web tech itself but rather the average-person-using-a-computer tech.
And, well, not all bubbles go as well as that. See the cryptocurrency one, say. Or any of a number of _previous_ AI bubbles.