At no point in the PT or TCW is any indication given that Palps alone is responsible for the fall of the Republic. The Republic falls due to it being crippled by corruption and decay, exactly the reason real life governments fall, this has been well explained by Lucas along with all the other tropes based on real life in the OT and PT.
Really? That is the entirety of the PT. Palpatine is the puppet master behind everything that happens. He causes the blockade of Naboo so he can become chancellor. He causes the clone war so he can destabilize the republic and destroy the Jedi. He has his hook in Anakin from TPM on. Palpatine single handedly does all this through his manipulations. There is debate as to who ordered the clone army, but Palpatine took it over, had Jango Fett selected as the source, implanted order 66. So for 3 years there were over a million ticking timebombs ready to destroy the Jedi when the order was given.
And where they went with TROS brought that puppeteering back, placing Palpatine behind Snoke. And Palpatine did die, but has been brought back by his Sith acolytes. In ROTJ they decapitate the Empire, sending it into confusion. But Palpatine had planned for that and his loyalists brought him back and the confrontation with Rey was supposed to be his final rebirth, but he was thwarted at last. In TROS the First Order and the other remnants of the Empire are not beheaded, they are annihilated. Palpatine is gone and there is no one to bring him back. Watch ROTJ. For Luke it all becomes about saving his father. For Anakin, as he comes back, it is about saving his son. Palpatine dies and the Empire crumbles. All around success. The force is in balance until the Sith resurrect Palpatine and he send Snoke into the world to act for him. Snoke and Dooku are playing the same role. Rey is the Force balancing the return of Palpatine. It does nothing to alter the OT or PT. That story stays intact. Palpatine was dead and the force was in balance. Anakin was the Chosen One. Rey is a new chosen one to reseal what the Sith had reopened.
And if you don’t think that works, you aren’t really aware of the myths that lie at the heart of Star Wars. Myths that always had sequels for a new generation of listeners. Books and movies have always had sequels. Often by the original creator, but often by others. And not every story was written in order. Some jump around. Hornblower and Narnia for instance. And frankly, everything I’ve heard about Lucas’s plan for the sequel has not sounded like a great idea. Sequels can build on the original and even restart things thought settled in the original. That is what sequels do.