There were a ton of hosts back then, but there still are. I don't remember exactly when registrars became a concept, i'd guess that might have been 1999 though; I don't think there's that many more or less now. A lot more registries with .ninja and .bike and whatever.
I agree though, if law enforcement wanted your domain back then, it would be about the same as now. Although, maybe someone would have called/emailed you about it with whois contacts back then.
Actually it might just be easier to link to the Wikipedia article about ISPs serving the US because there are a lot: https://en.wikipedia.org/wiki/List_of_broadband_providers_in...
Sorry, one of my pet peeves is when people say "the Web of [insert time here] is dead!" when the Web has never been more accessible both from a consumer standpoint and from a developer standpoint. The existence of Facebook and Google can be completely ignored if you actually want to. Emphasis on if you actually want to.
Again, it all comes back to the idea of some people "wish" the web of the 2000s still existed, but aren't willing to sacrifice the comforts of the 2010's web to make it happen. You can host your own lightweight website but Wordpress and Facebook is easier. You can search the web without tracking and Javascript but the modern websites don't work without it. You can pick from a huge variety of ISPs but they won't all be at 100 Mbps. Basically, you can have the web of the 2000s, but it comes at the cost of some of the conveniences of the 2010s web. A lot of people aren't willing to make that trade.
Nostalgia is hard. It seemed amazing back then but not many people would choose to go back to dial-up and phpMyAdmin. For those who say they would... what's stopping you? It all still exists today.
Of course many people could fill out the ICANN paperwork themselves and run a server from their own home, but many people can do that now too. And if you do that, you still run into the issue of hackers being able to install malware on your systems. But instead of the police seizing your domain, they kick in your door in the middle of the night with guns pointed at your family.
Maybe it would clear things up if you could lay out for me the exact scenario that combines "the web of the 2000s is rapidly disappearing" with "registrar, ISP, and hosting provider centralization is the issue" and ends with "if that wasn't the case, this website would never have had to shut down". I feel like you're remembering the web of the 2000s very VERY differently than I am.