Gameplay was a lot better, which is paired with the novelty of some of the systems (i.e.: change from Challenge Modes to M+, evolution of Apexis Dailies to World Quests, etc.). Since then most classes/specs have not received adequate redesigns since being gutted post Legion (i.e.: Fire mage is one of the most notable) and systems that had been iteratively developed have stagnated and received little to no refinement. This is to say that Legion is remembered fondly because even though it had some fundamental problems it still delivered refinements and improvements upon previous content and addressed issues with them.