A lot of people said that Cata was the worst WoW expansion set. We're at the end of MoP right now so I wonder if people changed their minds.
I personally didn't. Cata compared to MoP is terrible for me. It didn't have any end-game content besides dungeons and raids. MoP has tons of factions, world bosses, events, scenarios, flexible raids, brawler's guild, pet battles. Cata compared to MoP is shit.