They may have been voted best team, but they weren't. Their reasoning is poor in defending the honor. "Nobody gave it to us, we worked hard, we earned it." It's very nice that you worked hard. However lots of teams have worked hard, and that doesn't make them best. No one has ever said the '72 Dolphins didn't work hard or were terrible. That's a straw man.
Having been undefeated is a very good thing, but it's not the only thing. Did you beat other good teams, or was your competition weak? Did you beat other teams decisively, or just get by some of them? Was your magical season bookended by other good seasons with essentially the same coaches and players, illustrating that it was not a fluke, or were you just a very good team that also had some luck?
Just for openers, teams are much better now than they were then.