The problem is that there is no real definition of the old Internet. All we know is what it isn't. It isn't facebook, it isn't twitter, it isn't tiktok. Also, it isn't decentralized in the new sense of the word.
The old Internet is not a page with flashing colors and dancing babies, you can still create those today. It isn't geocities, or its newer counterpart neocities either.
The old internet is people making their own website. It's old because people surfing on the web today think that having a website is a business decision. Before it was just cool to own one.