I don't want to speak ill of them because they're doing an amazing job, but the Internet Archive doesn't have everything (especially old, long gone and/or obscure sites), isn't always complete, and often doesn't have things that back in the day that were on FTP sites. Sometimes you get lucky, but I've not had great luck there.
If you're maintaining some repository of information others find useful, please-please-please have a plan to pass it on to a successor caretaker and a notation in your will about your wishes.
I'm well aware of that, sadly. But often, part of "maintaining" a valuable repository of information (especially one that has reached stability and is not seeing ongoing updates) is uploading it to the Archive yourself. The Internet Archive has "trouble" dealing with information in the gigabytes and terabytes (which is why donations to them are valuable) but retrocomputing stuff is not like that.
part of "maintaining" a valuable repository of information... is uploading it to the Archive yourself
The problem is that we're talking about information that started suffering from bitrot before the Internet Archive became a big thing. Or even before the Internet Archive existed. Heck 99.999% of it existed before the internet.
Sure, it would have been great if on May 13, 1996 someone would have uploaded all of the information that there has ever been about the TRS-80 Model 100 to IA, but that didn't happen.
So often in places like HN the answer to flaws is "Well, you should have...," as if that solves the problem, or makes it go away. But it doesn't. It just makes the person writing that look like a jerk who isn't interested in solving problems, but in pointing out the failings of others.
If you're maintaining some repository of information others find useful, please-please-please have a plan to pass it on to a successor caretaker and a notation in your will about your wishes.