I heard that the new expansion is good and you don't have to miss WoW if you go and buy it :^)
I played for competitive PvP, no point returning to WoW.. It's literally balls, few friends who I played it with still play but they all turned to PvM. The expansions killed it for me, deleted a load of abilities so now it's just boring af.
Wotlk/Cata - Were the only expansions I enjoyed tbh,
5.0.5 MoP was a fun patch, especially as a healer because knowing how to survive required a lot, seeing how a lot of classes were able to 1-2hit healers.