The man hated by SJWs in tabletop RPGs talks monotheism, D&D, and why most D&D settings such because it lacks that thing despite all of the other trappings.
You know you've got something worth watching when you get a comment like this: "Yes. Monotheism is the missing link that D&D needs for a medieval authentic feeling in your game. I use it. In addition it does one of two things. It either keeps SJWs away from your game, or it attracts them because they want to break your game or be an antichurch outsider. In those cases they always end up quitting because they don’t get what they want."
That man--one Iron Cross--is not wrong. It is a good and effective filter; what SJWs you get will be the more cunning subversive sorts, in which case the go-to play is to call them out, confront them on their bullshit, and tell them to stop being shitters or get punted.
But it's another comment that really poured salt into the wound: "Wouldn't traditional Germanic polytheism scare SJWs away too, what with all the traditional gender roles like women being masters of the home but men being prominent in hunting, war, and government ? Oh who am I kidding, anything traditionally European makes these guys squirm."
First, that man--one CptMorgan252--is correct. Second, it is also true that you can count the D&D settings that even try to create an authentic non-Christian environment on one hand and you'll have digits left over, and those few attempts are less than half-assed; most RPG designers are not well-read, or properly educated, so they lack the skill as well as the knowledge required to do so. That some manage to do it, however flawed, is entirely by accident. Third, the notable examples of RPGs that did try to do so might as well be dictionary examples of "critical darling" and "cult favorite": Runequest as well as anything non-Christian-yet-historical (e.g. Bushido) are your go-to examples.
I could go on about the degradation of Christendom, and that does play into it, but let's look at a more immediate cause here: most people playing D&D could not give two shits about authentic (non-)monotheism. They're there to play a game, and they couldn't care less about the lore surrounding it. Therefore there's no benefit to putting in the work it would require for a commercial product to make it worthwhile.
Note the bold. I specifically mean this as a thing for commercial publishers to concern themselves with; hobbyists can do or do not as they will, since only their table matters and not the wider tabletop RPG audience/customer network. Despite this being a persistent thing since the 1970s, it is not something that cannot be surmounted; this is, in reality, entirely a failure of marketing. Put together a D&D campaign setting that's all about the Deus Vult and you'll have players saying that it's Time For A Crusade; make the game, not the setting, all about Making Christendom Great Again and you'll get a monotheism in D&D that actually works and players will actually care about.
Which brings me to how many RPG designers fail to comprehend what their job is, but that's for another post.