To Leucrotta, I don't really feel that anything you're saying here truly contradicts anything that I've said... but I do think that you are the one who is hanging onto something and wriggling to insist that that is the way it should be taken, contra to majority evidence. That's not intended to be an attack or to be abrasive, nor is anything else I say here, and I'm sorry if it comes off that way.
I've vetted myself through this a few times, and it still feels more argumentative than I want it to... but it's still a response I'd like to communicate somehow, so I'm going to spoiler it out in the hopes of not creating a derail. Please read it in the best of conversational spirits, or, if you feel we'd just end up arguing round in the same circles, don't read it and let it be, and I will too.
If we can write "Paladins get their powers from deities", and we instead choose to write "Most Paladins get their powers from deities", that changes the meaning of what we are saying, and pointing that out is not 'hanging on a word' or 'twisting a square peg' - It's pointing out a deliberate choice that was made with intent. Insisting - and please forgive my uncharitable paraphrasing - that "It really still just means what it used to before, that's what it actually still means. They just put that word in there for no real reason, it doesn't change anything" - That, to me, is wriggling, and hanging, and twisting. So please, take a step back and ask yourself why you are doing it.
If the answer is because the realms feel better to you if you think of them that way, or because you prefer it to work that way, that's fine - great even - but your feelings on how you'd prefer it to work doesn't have any impact on how it formally does, before home-table changes come into play. Recall that the examples you gave of those 'other' possibilities all existed in the era before the second sundering when paladins were still described in hard absolutes. They did not feel the need to write in non-absolute terms to account for those special story and novel exceptions at that time, because they were exceptions to a rule that was still absolute for everyone else. The change to non-absolute terminology that came with 5e was deliberate and unrelated to any of the specific individual special outliers described in other media.
If they wanted to stifle creativity and force players to follow absolutes in particular areas, then they would do so; they used to do so very firmly in earlier editions. Instead, since 5e and since the second sundering, they use non-absolute language, and they do so consistently; that isn't by chance or laziness. It's because that is the way it is post second sundering. This it does nothing whatsoever to impact the games of other folk at their own tables who wish to play deity-sworn paladins only - no-one, at any point, has ever suggested even remotely that it's normal or common for a paladin to not follow a deity. No-one, at any point, ever, has suggested that being sworn to a particular deity is anything other than the majority case in the realms.
However, it's not the absolute case any more - and it has not been for the past decade or so. If you don't want to play it that way, that's cool - but as written this is how the realms work now; they are not dealing in absolutes any more when it comes to sources of divine power.
"Deities and divine casters worked one way for literal decades until WoTC..." Exactly. - they did work that way... Until WotC pitched the next realms-shaking event, shifted the way the realms worked and altered the rules. They literally upended the realms, created the second sundering, rewrote many of the rules for how the realms operated. Direct god worship used to be the only way individuals could access divine power; now it is not. That's a change that happened. The realms were one way... but now they are not that way any more, and there are other possibilities.
As I said, this is not intended to be argumentative or taken in conflict, just as conversation. I don't really think we're going to be able to get to a place we agree upon - I can't convey to you why having those other possibilities, and allowing others to have those possibilities, matters, if they don't matter to you, but if that's where we are, that's okay.
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To answer your question - if we had deity selection for Paladins, and 'none' was not an option, yes, I would be exactly as adamant about them adding it as I am currently about them adding deity selection, with the option not to follow one included; I'd still want what I want, as adamantly as I want it, and object to the implementation that does not match that in just the same way.
Out of curiosity... how do you (or others) feel about divine soul sorcerers - they tap divine power to realise their magic, no deity required, and are completely official in the realms.