Don't underestimate how the 'meta' of a game can change even if the game itself would be static. A gaming community evolves, learns, adapts and discovers.

The game's fans have been playing competitively on private servers that preserved/recreated the pre-expansion releases all this time. Stepping into 5-person PvE in this Classic release might be a very different from how it was 15 years ago, even though the game mechanics itself were meticulously designed to be just like the original.