The Sequels add so much to the Star Wars story. They give an insight into a galaxy picking up the pieces in the wake of the fall of the Empire, and display the impact of the original heroes' deeds on the worlds around them. The villains, the First Order and the Knights of Ren, are framed as successors to Darth Vader and the Empire. The sequels introduce new powers of the Force, such as the Force link, Force projection, and Force healing. They even take a daring direction with the original hero, Luke Skywalker himself, by making him jaded and bitter before taking him on a final redemption arc. What did the Prequels really add to Star Wars? Besides showing off a few more Jedi, the Prequels didn't do much. What they did add was either obvious (the Clone Troopers that would become the Stormtroopers, for example), or poorly handled (Anakin's supposed tragic backstory was more annoying than tear-jerking). Since they were Prequels, their content was inherently limited to simply lead to what was in the originals. On the other hand, the Sequels, being sequels, had more room to tread new ground. And tread that ground they did. The Sequels showed that the creators were willing to expand on the content from the originals, and take the story in a direction that fans hadn't seen before. They were uniquely positioned to define the "new" Star Wars. The Prequels, by contrast, were inherently limited in how much they could add. Whereas the Prequels could only serve to point back to the originals, the Sequels freely entered uncharted territory, and added a wealth of new content to the Star Wars saga. The Sequels are superior to the Prequels in every way.
The Sequels added to Star Wars in a way that was poorly executed. Its post-Original Trilogy setup was just the Original Trilogy all over again: an evil government and a rebel group, using the same weapons, ships, and uniforms as the original players. Their character exploration was poorly justified. Why does Han Solo, a new hero of the Rebellion and the spouse of royalty, go back to smuggling again? Why does Luke Skywalker, the most optimistic of the Jedi who redeemed Darth Vader, try to kill his nephew? And the Force powers they introduced ruin the concept of the Force. Force healing cheapens the deaths of all the Jedi who came before, and died because Disney hadn't written Force healing yet. The Prequels created a universe that was markedly different from that of the originals. They introduced real, living worlds, entirely new villains, and visually unique characters. One would think that the Sequels, taking place after the original trilogy, would show how the galaxy had changed. But instead, they ended up reusing the same basic formula, and missing badly when they tried to innovate.