Popular speech. Democracy. What is going on here? "Are you saying, man, that literature has influenced the devolution of power through the ages? Is that it? Be clear!" Well Dante was self-consciously working in the tradition of Virgil, the most revered poet of the Roman oligarchs and despots - whose organs of power (the Church, the Law) contemporary elites still in his day relied on to continue to govern Europe - so you could say that by writing his Commedia in the vernacular he was handing a petition to those in power on behalf of the popolo, the plebs. a document of such persuasive power that, combined with the technology of printing, its message resulted in generations of civil conflict in Europe that would change the world in uncountable ways, one of which was to be that all English boys received a classical education. And so enter Shakespeare, who grew up in what was effectively a cultural backwater but who had access to all the resources of millennia of learning. And the little bastard could read them.
And it's no surprise that he emerged in the place where power had devolved away from the despot to the greatest degree imaginable at the time: in England. Without discounting his hit-the-ground-running early plays and strong female roles it's in his late masterpieces such as Hamlet that we see the emergence of the individual as a new cultural species. Sure, there were other innovations appearing at the same time, particularly in the great proto-novels of Cervantes where again it's the individual who struggles to emerge amid the restrictive structures of contemporary social modalities, but if you want to talk about greatness you have to acknowledge the lifetime achievement of the Bard because of the sheer bloody influence it wielded in successive generations: just go into any large university library that still makes its historical holdings available to see how many annotated editions of Shakespeare there were in the centuries since his death.
In England bardolatry was so prevalent that for generations publishers and their hired pens "cleaned up" Shakespeare's language - because there were so many infelicities there, don't you know, dear chap - so that it wasn't until around the time of the American War of Independence that accurate editions became available. Jane Austen was born the year before the Declaration of Independence was drafted and signed, and it is within the heated morass of debate about the rights and privileges of the individual that she developed her ideas about writing that were to emerge in the first recognisably modern novels, so modern in fact that millions of people still read them today. Again, as in Shakespeare's case, it's not surprising that Austen emerged at a time of violent discussion about who should hold power and what would happen if power was devolved away from the despot into the hands of the popolo, the plebs. The women!