Them ignoring the fanboy minutia ISN'T bad writing, it's them understanding that to 99% of people who watched the film they didn't notice or didn't care because they see that the film is about bigger things than that.
I can't speak for others, but I certainly didn't allude to or was bound by any kind of fanboy minutia or subjective expectations; I deliberately didn't refer to anything specific because others have already done that very comprehensively.
Let me be more clear about where I think the sequels have employed bad writing and creativity independent of any kind of fantasy lore or fanboy expectations.
- Stormtrooper indoctrinated and trained from a very young age suddenly has a pang of conscience on his first mission, develops a sense of humour and clumsiness and quickly joins the resistance. Do you really think that character arc couldn't have been better-written?
- Dyed-in-the-wool First Order stalwart Captain Phasma agrees to turn down shields at gunpoint without so much as a struggle or fight. This is a woman whom we had earlier seen massacre a village in the name of the First Order; surely she'd rather die or be tortured than just go "yeah, sure, I'll turn off those shields because three of you guys told me to". Again, if the writers really needed to get to a point in the story where the shields were deactivated, is that the best they could come up with?
- Luke Skywalker sees a glimmer of good in Darth Vader and would rather die trying to bring it out of him (over the course of two movies!) than give up and join the Emporer. Years later an older and wiser Luke suspects a bit of darkness in his nephew and considers murdering him in his sleep, because the writers needed a way to explain why he became a hermit and why Ben Solo became Kylo Ren. Do you think that's good writing? Mark Hammill certainly didn't think so.
- Finn and Rose attempt to help the Resistance escape destruction (because it ran out of fuel...). They end up at some interstellar Monte Carlo where they fail to contact the person they were sent there to contact, only to be conveniently aided by a smart con man who appears out of thin air (deus ex machina) and screws them over just as we all knew he would. That entire subplot feels like an RPG side mission where nothing makes sense and has no impact on the actual story. It was long, dull and unnecessary. As George Orwell always said, if something could potentially be easily cut then it shouldn't be in there in the first place.
Four examples of bad writing that have nothing to do with fanboyism. They don't even have anything to do with Star Wars - you could replace 'Stormtrooper' with Franco soldier in the Spanish Civil War, Captain Phasma with Radovan Karadžić and so on, and you'd still have badly written subplots and character arcs. The context - Star Wars - is irrelevant and thus so is fanboyism.
Rogue One's plots and character developments made sense - using the same source materials and the same 'universe'...and with the same 'fanboys'.