The biggest difference in the landscape is the postseason structure.

No playoffs in 1984, so the argument is whether BYU should have been ranked #1.  Considering BYU's record that year by itself is misleading because the main reason BYU deserved to be ranked #1 was that every single other team failed.  BYU would likely not have been ranked #1 in almost any other year because it was unusual to have every single other top team fail.

Today, arguing about being ranked #1 is immaterial.  The argument is about being ranked Top-4 to get into the playoffs.  It's a totally different argument.