Except, again looking at Star Wars/A New Hope, they mention an Old Republic. What happened to that Old Republic? Why is there a senate to be dissolved if this Republic has been gone for so long? Is the Empire new? How’s it gain so much power so quickly?
Snoke doesn’t undo anything of the original trilogy. Palpatine not being defeated does, but a new threat coming from the Unknown Regions does not.
It’s not any more or less established in universe, your need for every answer coming from a 30 year gap is not the same as a flaw in storytelling.
For me, it comes down to how unlike a first installment, typically sequels continue the story of their predecessors. You can start midway through a backstory for a first movie, but a sequel? It’s just confusing and makes the first movie feel redundant. Imagine in Episode V’s crawl opened with the New Republic many years after the defeat of the Empire. It wouldn’t make any sense and would make ANH feel pointless in retrospect.
I’m not opposed to Snoke appearing, but it’s so upsetting to watch all of the OT, watch the ending celebration, and be hyped to see a New Republic victorious… and that never happens. We just reset to a Resistance / Empire dynamic again. It feels like there’s a trilogy missing to bridge this gap.
(That said this isn’t something we can fix in fanedits… the best we can do is try to explain who Snoke exactly is to give it some semblance of cohesiveness).