I want a have a comprehensive set of playable D&D 5e rules − that dont refer to polytheism in any way, shape, or form.
So, I should just delete the references from the 5e products that are already out.
Easy, yes? No.
Besides the normal situation of any world-building requiring enormous work, and inconvenient issues like trying to edit a pdf, here is the situation.
The legal department at WotC intentionally created two tracks for how to use the D&D 5e system.
One track is, you must use the Forgotten Realms setting (with all of its polytheism), and if you do, you can freely access everything else in all the other 5e publications, the entire Players Handbook, the Elemental pdf, the DMG, the Monster Manual and other monster books, the Sword Coast and other setting publications, all the adventures, everything that WotC has to offer. You can even make money if you contribute to the Forgotten Realms setting, selling your work in the DMs Guild. As long as the work conforms to this world of polytheism, you have a wealth of resources to enjoy.
If, on the other track, you are creating your own homebrew campaign setting, too different from the Forgotten Realms setting, then you get bare bones. The 5e SRD pdf. And that is it.
Of course, if all of your efforts are strictly for your own personal use, you can do what you want.
But if the work that you are doing for your campaign world, is serious, longterm, public, or who knows, later monetizable, then you need to be careful about the legal status of what you are doing. You cannot mix your homebrew setting with *any* IP content in any D&D 5e product, except the 5e SRD. Because. If you do, the D&D police really will come to your door, and tell you that you are doing it wrong. Namely, the WotC lawyers with cease-and-desists, or worse.
I understand why WotC is doing this. It is a good business model, compromising between complex issues, mostly for mutual benefit.
The problem is. There is no safety valve for me. The only WotC setting that is legally permissible at this time is Forgotten Realms. It is precisely the setting that I dont want because of its polytheism. So have no access any D&D 5e product but the SRD.
For example, the only feat that I am allowed to use in my homebrew monotheistic setting, is the Grappler feat. I have to make up all of my own feats.
And the only background that I am legally allowed to use for my monotheistic setting, is the Acolyte background that says the character is a polytheist who is especially dedicated to a ‘pantheon’ of gods. Heh, how annoying is that!
All of the classic D&D spells are in the SRD, yet I look at the Elemental adventure spells that I like that I cannot use. I will have to design my own elemental spells.
In order to make my monotheistic campaign happen, I have to build mostly everything from scratch, honoring the same legal conditions that indy publishers have to comply with.
At this time, it is not my plan to become an indy designer. I just want to play some D&D. Any effort that do towards this play, I want to freely share with others.
This is an overwhelming investment, just to play a game.
I just want a campaign setting that has nothing to do with gods. And it is really is hard to do.
I have to rewrite the entire set of rules from scratch.