Exactly this. I didn't play the expansions but I heard about the Jailer. And fucking Uther comes back to life or something?
Basically the problem is that nothing means anything anymore. If something happens, it is just made to un-happen later on. After Arthas, the Lich King, the master of the Scourge, and aside from the Titans themselves the most powerful single entity in the WC universe, meets his demise at the hands of ten nameless Mountain Dew-drinking twats, the ghost of Uther tells you that without a Lich King the scourge would become an unstoppable force.
Which makes no fucking sense because the whole premise was that the undead were just scattered, one-off instances of rogue necromancy. The thing that made them a threat to both the Alliance and the Horde was their unity under Ner'Zhul. The Scourge was a manageable foe by itself, used only as a tool by the Legion. The Burning Legion feared its own creation at the thought of it being unified under one spirit.
The more they write this shit-fest the dumber it gets. "There must always be a Lich King." No, there mustn't, you fart nugget.