I think perhaps it's generally agreed that the greatest plot... hole?... issue?... mistake?... in Star Trek is transporter technology, which is far too powerful as it's shown to work to bring people back from the dead (TNG), and I think also at some point alter their DNA (am I remembering that one right? Not that it matters, though, the back-from-the-dead ability, which obviously includes cloning/photocopying people implicitly, is bad enough). This is an ability which, as widespread as the technology is, would make monumental, fundamental changes to society that it... hasn't, because when they wrote that in nobody thought of it, and because fixing it after the fact would be pretty impossible, leaving no choice but to kinda ignore it.
I think droid rights/droid slavery is kind of this issue in Star Wars. It looks like that even being an issue was accidental and that nobody ever really thought it through at all? But it also feels like a fundamentally stupider error, because nobody accidentally wrote it in after the fact - you're talking about core characters written as sentient and sapient, memorable plot points about buying and selling them and then no other attempt to deal with it. I mean, maybe throwaway mentions of the existence of a droid rights movement was someone's idea of fixing it, but it doesn't work when the attention paid by the main characters (and the good characters) is so minimal. Even if it's intended to be a little horrifying perhaps - though I don't think it is - it doesn't work on sheer believability for me, because, you know, in human history, slavery (and other stuff like ethnic cleansings) at their worst and most widely-accepted state still had plenty of opponents. I suppose there's an argument that could be made that the lack of acknowledgement and support for that movement is explained by humans' natural lower empathy for non-human beings, but I don't buy it. (And also I don't buy that it was intentional.) Then there's the absolute disaster of the Han Solo prequel movie's treatment of the issue (although that can't be held against the rest of canon of course, but I think it adequately demonstrates that the modern era has nobody with a clue at the wheel in a supervisory capacity).
I think droid rights/droid slavery is kind of this issue in Star Wars. It looks like that even being an issue was accidental and that nobody ever really thought it through at all? But it also feels like a fundamentally stupider error, because nobody accidentally wrote it in after the fact - you're talking about core characters written as sentient and sapient, memorable plot points about buying and selling them and then no other attempt to deal with it. I mean, maybe throwaway mentions of the existence of a droid rights movement was someone's idea of fixing it, but it doesn't work when the attention paid by the main characters (and the good characters) is so minimal. Even if it's intended to be a little horrifying perhaps - though I don't think it is - it doesn't work on sheer believability for me, because, you know, in human history, slavery (and other stuff like ethnic cleansings) at their worst and most widely-accepted state still had plenty of opponents. I suppose there's an argument that could be made that the lack of acknowledgement and support for that movement is explained by humans' natural lower empathy for non-human beings, but I don't buy it. (And also I don't buy that it was intentional.) Then there's the absolute disaster of the Han Solo prequel movie's treatment of the issue (although that can't be held against the rest of canon of course, but I think it adequately demonstrates that the modern era has nobody with a clue at the wheel in a supervisory capacity).