If only the EU authors could write stories set in OT-only parallel universes…
Well, you can always do it yourself. The main problem is that you can’t sell it.
However: since most places/things/people are never named or explained in the OT you could easily write and sell books about the OT with the serial numbers filed off - use the script names like ‘Laser Sword’, change a couple of terms (Jedi, the Force) and don’t refer to named characters (or change their names) and there’s basically nothing in Star Wars you can’t use/base your stories off of. Most of it is pretty generic Flash Gordon/Knights and Princesses fiction, so there’s essentially no way they can prove you’re copying them if you don’t use specific trademarked names.
Darth Vader is halfway a Doctor Doom knockoff, the ‘Empire’ is the most generic and un-trademarkable word for a government in history, ‘Senate’ and ‘Republic’ likewise. There’s not a whole lot original in Star Wars, and if you ignore the toys/EU/Pre/Sequels there’s even less that can possibly be nailed down as IP infringement. In fact I am sure there are some published sci-fi novels that are ‘Star Wars with Serial Numbers Filed Off, Author’s Personal Canon Edition’.
The Stellar Strife, where the remnants of a feudal republic attempt to revive the vision of a free society against the galaxy spanning empire that has replaced them and ignite a civil war.
Rebels can’t be TM’d, you can say ‘alliance of rebels’ or ‘insurrection movement’ instead of Rebel Alliance and there’s no way to prove you’re using Star Wars as a basis, etc.
Star Wars is much easier than Star Trek to create analogues of, because almost all the terms, storylines and characters in it are super-generic stuff that’s been recycled a million times. In fact (while I do like Star Wars) it’s more of an example of an especially well done knock off of Flash Gordon and medieval romances than anything particularly innovative. It’s just that most people know Star Wars much better than the source material it cribs from. In terms of unique, original, innovative and plain weird stories there is a lot of stuff published in the 20s-40s as sci-fi and sword & planet fiction that’s quite a bit less generic and predictable than Star Wars as a story line or terminological mine. In fact part of the reason Star Wars probably does so well is because its terms, plots and memes are super generic and thus easy for people to identify with. Cordwainer Smith requires quite a bit more mental effort and obscurantist tastes than ‘old knight teaches Chosen One how to defeat the Evil Wizard, Rescue the Princess and fight the Black Knight with the help of a Charming Rogue.’
And what could possibly be more generic a religious/magical term than ‘The Force’, or (for the black magic version) ‘the Dark Side’? It sounds like someone took a real science fiction story and replaced every single specific name for institutions, technology, and places and replaced it with the most generic possible term for that general class of things. Most real religious orders, magical systems, fighting aristocracies, etc. have very specific names and pretty detailed histories and beliefs, throw out all the specifics like that and you end up with something very much like Star Wars.
Instead of the Hospitaller warrior monks being named Supremus Ordo Militaris Hospitalis Sancti Ioannis Hierosolymitani Rhodius et Melitensis they’re just called ‘The Knights’.
In fact this happens in real life, so you can also infer that the ‘Empire’ and ‘the Knights’ and ‘the Rebel Alliance’ actually do have specific names reflecting their origin and orientation, but are simply called these things as shorthand (especially by their enemies and outsiders). So if you actually invent specific names, motives and origins for these institutions and practices you have gone further than Lucas (or most of the EU) in actually making them realistic/versimilitudinous.
The biggest downside is that you can’t automatically sell things to kids and nerds by slapping the STAR WARS brand on it, but if your objective were to write good Star Wars stories instead of making money for Disney there’s basically nothing stopping you.