We’ve been telling you this for 6 months. Vanilla endgame content was very easy. It will not be a challenge to anyone who’s done mythic raiding or high M+ in current WoW. The difficulty is closer to LFR than it is to current Heroic raiding. This is how easy it always was. People were just terrible at playing WoW in 2004.
This is why multiple difficulties were added to the game to begin with.