Y'all know the drill here - this is a speculative jam. Nothing in this is to be taken as what Blizzard is actually saying.
In the distant past, Azeroth was formed by the hands of beings potent even beyond gods. These beings, known to us as Titans, have left the evidence of their presence in many ways - huge, magnificent complexes of astonishing construction, races shaped by their will, the prisons that held Yogg-Saron and Y'Shaarj's heart, and much more besides. From the Mogu'shan Vaults to Uldaman, from the fantastic jungles of Un'Goro to the Sholozar Basin, including the magnificent Vale of Eternal Blossoms the Titans left their mark in the very structure of Azeroth.
Recently the black dragon Wrathion consumed the heart of Lei Shen the Thunder King, a mogu warlord empowered by the stolen power and knowledge of Master Ra (known as Ra-Den to them), a Titan Watcher similar to those left behind in Ulduar. When he did that, he spoke the following words: "We have fallen. We must rebuild the Final Titan. Do not forget." I've wondered long and hard what that could mean. But it wasn't until I considered the powers the Titans bestowed upon the five Dragon Aspects so long ago. Their control of life, magic, dreams, the very land beneath our feet and time's ebb and flow was so absolute that it beggars the imagination, and it also asks us a question - could they bestow this power, if they did not have it themselves, and more besides?
We casually discuss the vast oceans of time that separate us from the Titans. Untold tens of thousands of years, perhaps more - indeed, none can say exactly how far in the past the Titans began their ordering of the universe, much less arrived to create Azeroth. Sargeras had already fallen to be the Dark Titan over 25,000 years ago, but how far before that is unknown to us. But it brings a question to mind - how could such powerful entities seemingly vanish? Why have they left their creations to their own devices? Why are emissaries such as Algalon watching over their creation, rather than the Titans themselves? Is it merely that they are so distant from mundane mortal concerns, living on a scale vastly beyond our comprehension?
I submit it is something else entirely. To determine what, we must look at their actions, and the servants they've chosen to enact their will.