Is most of that data because of there being like a zillion different views and sortings of the same posts? That’s been the main difficulty for me when wanting to crawl some sites. There’s like an infinite number of permutations of URLs with different parameters because every page has a bunch of different link with auto-generated URL parameters for various things, that results in often retrieving the same data over and over and over again throughout an attempted crawl. And sometimes URL parameters are needed and sometimes not so it’s not like you can just strip all URL parameters either.

So then you start adding things to your crawler like, starting with shortest URLs first, and then maybe you make it so whenever you pick the next URL to visit it will take one that is most different from what you’ve seen so far. And after that you start adding super specific rules for different paths of a specific site.

Also less useful because the web is so easy to access, I remember using it back then to draw things down over the university link for reference in my room (1st year, no network access at all in rooms) or house (or per-minute costed modem access).

Sites can vanish easily of course still these days, so having a local copy could be a bonus, but they just as likely go out of date or get replaced, and if not are usually archived elsewhere already.