For you, what aspect of the game is extremely close to being perfect (or as perfect as possible), and only needs a tiny adjustment or change to make it so? (Whether it's related to raiding, mythic+, pvp, RP, lore, questing, graphics/technical stuff, etc.)
For example, I care a lot about aesthetics/RP/immersion stuff, so I'll start with one of mine.
1. I think that Worgen are the one of the coolest things Blizzard has ever introduced to the game. Giving Worgen melee classes the option to transmog to "invisible" weapons (like monks currently have), and/or giving Worgen druids the ability to use their Worgen form for their feral/guardian form, is all that's needed to complete the werewolf fantasy. It's like, so close, but not quite there.