Michael Douglas' digital de-aging is a revolutionary breakthrough in special effects, while Downey Jr. is more noticeably off in comparison but still vastly superior to digital de-aging done even less than ten years ago and certainly less cartoony than Carrie Fisher's de-aging.
Ok, considering what we see of the Empire's inner workings and the destructively jealous mindset of its top brass in the events of Rogue One the Galactic Empire's chance for being a stable, durable regime was pretty much fecked as soon as A New Hope and was trapped in a economic/political/military death spiral before the Battle of Endor commenced. The Galactic Empire had frittered away much of its legitimacy and popular support (this shrinking goodwill permanently blown away with Alderaan), got bogged down in millions of insurgency campaigns throughout the Galaxy and had its Navy unable to hold down the systems everywhere, and so the Imperials became fatally fixated on the Death Star, a symbol for their own fear of losing control really, rather than a symbol of power.
The Death Star blowing up was a huge body blow the reeling Empire never quite recovered from and it was on borrowed time from that point on. And even if the Death Star repelled the Rebel attack at Yavin it was ultimately only a glorified giant hammer that would only work in the short term to suppress the intangible ongoing crisis of the galactic population's growing unease and dislike at Emperor Palpatine's one sided authority. Palpatine was forced to build a second Death Star to vainly shore up his rapidly crumbling credibility, even if his minions were probably unable to fully finish it (and perhaps why it was expended as bait at Endor).
And elderly and dysfunctional as the Senate was, Palpatine dismantling the Old Republic's institutions and re-distributing direct authority amongst his loyal Moffs and Grand Moffs to protect his absolute power was a paradox (shared with real life dictatorships) of the Galactic Empire sowing confusion while trying to impose order, having a horizontal military thugocracy that encouraged fiefdoms and squabbling (when you had the Empire's chain of command inhabited by magnates like Tarkin, Vader, Jerjerrod, Motti, and Krennic who couldn't stand the sight of each other), a relatively chaotic system which would no doubt erupt into open fighting once Palpatine was no longer at the wheel...