In short, it is beginning to feel like good faith attempts aren't good enough and some topics should best be avoided so as to not invite controversy.
But, that's not really true though. Good faith attempts are most certainly good enough. No one is saying that Gygax and Cook are raging bigots for writing OA. Just that, thirty some years later, what was a good faith attempt then isn't really good enough now. Viewpoints change as more information comes to the fore and society's view of these changes also change.
IOW, there are all sorts of very good faith arguments about, say, the changes in orcs to make them more inclusive. Most of the people really are discussing in good faith.
But, you have to ask yourself, (and by yourself, I mean everyone, not just you), is the point I'm bringing up ACTUALLY an issue or is it something hypothetical? If no one is actually arguing that orcs should not be evil, then maybe, bringing up orc alignment isn't really the issue at hand. Actually drilling down to the real issue at hand is where the boundaries are.
Actually, to be fair, there are no "boundaries". Trying to define "boundaries" as in, "This is okay and that is not okay" is a rabbit hole in and of itself. Stop trying to make a general statement and focus on the real issues and you'll find that conversation is so much more productive. Identify what the real problem is with something, and then address THAT problem. Stop trying to make rules for everything. It won't work. Every element is different and there is considerable nuance.
Take the the Appendix E argument - should the authors in Appendix E be there or not? Now,
@Cadence mentioned Lieber. I'm not aware of any issue regarding Leiber's writing. He doesn't come up at all and, in fact, I would generally hold up Leiber as being probably one of the best examples of a writer from the Golden Age that we can hold up as inspirational. Leiber's writing and his personal life, AFAIK (and please correct me if I'm wrong) haven't been an issue before, so, I have no idea why he would be a problem now.
OTOH, Lovecraft most certainly IS problematic. His fiction and his personal life are rife with bigotry and intollerance. When he talks about the fish eyed abominations in Shadows of Innsmouth, he is SPECIFICALLY talking about my children. So, yeah, I'd say I have a fairly large problem with his inclusion in Appendix E. I would much rather see him removed. Now, why Lovecraft and not,say, Howard? Well, sure, Howard and Burroughs aren't exactly the epitome of cultural sensitivity, but, let's be honest, they are both more simply reflective of their times. Howard and Burroughs don't really go out of their way to attack various minorities in the way that Lovecraft does.
So, for me, I'd remove Lovecraft from Appendix E, but, Howard and Burroughs can stay. Maybe add a sidebar noting the issues with them, but, that's not a major problem. Outright racist writing, or, like the descriptions in orcs, writing that mirrors outright racists, should probably not be enshrined in the game or placed in a position of honor with "Inspirational Reading."