The specific example that made me start thinking about this was how AC Odyssey has a sidequest where a slave doesn't want to be freed because he thinks being a slave is cool, actually, which is both absurd apologetics but also misses that in Greek and Roman systems manumission was a form of social control that both rewarded and indebted slavers' most loyal collaborators. That turned into thinking about how just absolutely absurdly shitty classic Greek society was in general, and how AC Odyssey made it this weird wholesome egalitarian slaver dictatorship where everything's cool and good except for the bad mean guys who are indistinguishable in methods or goals from anyone else.
That's also one of the things that pisses me off about Starfield so much, how the "good guys" are a pair of far right colonial empires: one is literally just the fascists from Starship Troopers, and the other are a bunch of feudal ancap dictatorships. Even the villains are just saturday morning cartoon villains who are bad and mean but don't really ever do anything distinct from the "good" factions except be ontologically opposed to you, the main character.
Someone else pointed out recently how HOI4 ends up effectively doing Nazi apologetics the same way, where in trying to avoid giving their worst fans a holocaust button they just outright remove all the actual horror and material actions the Nazis did altogether.
And I don't think I even need to get into how rampant this problem is in liberal fantasy settings, which are always full of apologetics for monarchism, because that's well tread ground for criticism. It's enough to make something like how the original Mount and Blade handled the in-universe nobles as being inherently sexist and classist pieces of shit who were obstacles for a female and/or commoner PC to fight against and overcome almost refreshing, instead of it just being like "yeah these awful pieces of shit who are all definitely mass murderers and worse are actually cool and nice to you and not really all that bad really" like so much feudal apologia media does.
And yeah, there's a point to be made about not wanting to grapple with problematic themes and all, but where there's the line where that just turns into apologetics for the very problematic thing you're trying to avoid dealing with at all?
I'm trying to think about what it is that really bothers me about it, and while the whole essay about diegetic essentialism and how one really shouldn't look at fiction as if it it's coherent and real even diegetically is stuck in my head I can't help but think maybe that bit of literary theory is incomplete. Like I'd almost want to call my perspective on this "diegetic materialism" as the idea that when creating or depicting systems in fiction they should adhere to the same material pressures they would if they were real, that if you've got a system based on stratification and elitism that it should actually be realistically awful, that it should have the problems that inevitably follow from its structure. Like how in Starfield the hyper-stratified military dictatorship with massive interstellar corporations that just straight up denies basic rights to a supermajority of its population is also this nice tolerant society where there's poverty and dysfunction but none of the misery that goes along with that, none of the brutality that would be required to uphold it, none of the attitudes or hyper-exploitation that would lead to its specific system being designed in the first place - it's like an old Disney cartoon with happy singing serfs who like being the property of the fair and beautiful nobles because it's all just play and there are no material consequences to poverty at all.
For all that's to be said about author fiat and the fact that creators can just say "actually it's all fine and nice in my world," I can't help but feel like that's just doing "thermian propaganda" to copy the term someone else coined to describe it the last time I posted about it here, that the creator is effectively doing an intentional appeal to the thermian argument by constructing a world where [bad thing] actually is fine and good actually.
But then that line of thinking runs into the sort of issue you bring up there, that following this principle to its logical conclusion effectively means that a huge array of topics/settings effectively end up being locked to either "don't touch it at all" or "depict the living hell it must be" and we have to start getting into the question of the responsibility an author has to not normalize or do apologetics for [bad thing] by treating it too casually or nicely, and what the standard for "casual" is and how much the work has to explicitly and textually condemn it as bad, etc.
And I just don't have an answer for that despite thinking about it a lot while I'm writing.
Sorry, that was my criticism of my own point, that taking it to its logical conclusion ends up pigeon-holing a lot of things into either just not being done or having to be bleak and depressing pieces, which is obviously taking things too far because as you say, that becomes uninteresting and I'd expand on that to say that if played fully straight, if one really dove into capturing every facet of the shittiness of say Rome or a Roman-expy that it becomes reactionary just by repeating and not combatting the sorts of chauvinist perspectives that would dominate such a setting.
So clearly there has to be at least some anachronistic or otherwise out-of-place good in a work, because otherwise one is just uncritically reinforcing whatever is being depicted (like how 40K largely fails as satire because it's just "things are bad and [bad thing] is correct in this context because [thermian propaganda]" a lot of the time, and relies on the reader being able to say "oh no this is bad, actually" instead of gormlessly lapping it up). But add in too much good and decency and it effectively becomes propaganda instead, like when feudal dictatorships get a liberal coat of paint in fantasy writing.
Which ends up back at what I keep trying to answer myself: where does one draw the line, how much responsibility does an author have to draw the line in the right place, are there tricks to streamline this and make it simpler to comprehend? And every now and then I have the horrifying realization that I'm like two steps away from suggesting "what if the Hays Code, but communist, as a bit?" which moderates the line of thought but sends me back to the drawing board, so to speak.