It's only impressive if you've become accustomed to the unfortunate trend of forced obsolescence and the desire of many to justify useless recurring "maintenance" busywork. Basic HTML and CSS will always work.
I think the challenge is also caring enough to keep paying money to host a site for no clear purpose or gain. And moving hosting providers since guessing hostgator didn't exist back then. Based on the modified times on some assets on the site I'd guess it was last moved in Oct 2015. So glad they kept it up!
You can see it's been basically unchanged for 25 years! Here's the 2001 snapshot from the wayback machine: https://web.archive.org/web/20010202180000/https://britneysp...
Just keeping any site functional and up for so long is impressive by itself.