What I'm about to say is something I know you guys wouldn't consider it to be an unpopular opinion, but I do know if I were to say this anywhere else on The Internet, or heck anywhere on social media. I'd probably get a variety of reactions ranging from mixed to potentially heated ones which is this:
No Mutants Allowed & Duck and Cover are important to the legacy of both, the history of the Fallout series and it's fandom!
With the dedication of both websites shown through such things as:
Reporting news of whenever a new game was coming out, insight into the development process and what to expect for upcoming games through developer interviews, and by giving constructive criticism to developers(for certain Fallout games, it was during the time when they were still IN development) in which that it both helped the games to an extent, while other times it sadly fell on deaf ears.
One thing that I think is what's most important of all, is the fan reception of each Fallout game during their initial releases. Because whenever I look at the fanbase now and look back at what their perception was for each game, I usually use this website as point of reference. Like how people perceived Fallout Tactics back then compared to now, how certain people back when Fallout 3 first came out said that FO1 and 2 are games with crappy graphics and slow gameplay, now consider them(with New Vegas included) to be a lot better than 3, and of course how the many flaws that NMA pointed out about Bethesda have been finally realized by many a decade later with the release of 76. I've seen some people say that the OG fans from here were prophets! I was thinking the same thing too, that is until I started lurking through the archives of this website and of course, reading the masterpiece of The Glittering Gems of Hatred!
People may perceive these fansites(especially this one) as elitist echo chambers for bitter OG Fallout Fans, but for me. I'd say they're very important to the series legacy more than they realize it.