even if you don't binge and have "appropriate amount of gear", the content is still very easy. People that played during vanilla probably remember how many deadweight they carry in a 40man raid, while the not-as-dead-weight don't even know how to optimize their performance. Information being widely available for 15 years definitely is the biggest factor, and when many people's BIS (especially pre-MC) are just greens from the AH, it is very easy to gear up to a competitive level.
Things will be the same for AQ (nature resist gear is attainable outside of raid, if you even need it for Huhuran) and probably Naxx. Back in Vanilla I know you had to farm frost resist mats inside the instance to do Sapphiron, but heck, even that might have been bypassed on private servers already and deemed unnecessary.