You're arguing that it's not hard to proof the existence of the supernatural in the CV universe and that a large reason for this is because people don't want to open their eyes to the truth.
OK no, that's not what I said. I might have misrepresented myself somewhere. If so, apologies -- may this answer stand as the "canon" version of my thought process:
I DON'T think it's so easy to prove the supernatural in the CV universe, for many reasons: Enemies burst into flames leaving nothing behind, the Church has a stranglehold on information, it has agents to go and do "cleaning up", merely witnessing these monsters and escaping alive to tell the tale is in itself a feat not easily accomplished (unless you're goddamn Hammer apparently). And that's not getting to Dracula and how that much harder would be to prove HIM as real. And ALL of that ON TOP of people's own biases, which are by themselves incredibly powerful things.
Now, it's still possible. Just not that easy that flipping a rock proves the existence of a fairy. We NEED to understand that OUR perspective of the CV universe just happens to always be positioned where the supernatural action is taking place (which, in most of the games, is somewhere pretty isolated). But it being possible, then there are cults amassing hundreds of thousands of followers, just as Graham's modern 21th century cult.
Also let me say this: Celia summoned monsters in the middle of the street. Once. All of them burning into nothingness, in a battle lasting incredible 2 minutes. This is not something that happens everyday constantly. This is enough to AT MOST become a town rumor/urban legend to attract tourists.
My problem with your argument is this: you're starting from a position of "some people just don't believe in the supernatural, and wouldn't believe it even if the evidence stares them in the face", which only works in a world where magic doesn't actually exist.
People really want to believe in the supernatural and they don't stop until a total lack of evidence makes them, and then only grudgingly. If there is actual evidence then there would be no reason for unbelievers like Soma to be a thing. Yet, somehow this isn't the case. Meaning there must be a very damn good reason why the existence of the supernatural is disputed in CV's version of the modern era. And you can't explain this soley with the deniability argument or coverups.
Alright so, let's use one case closer to Soma (modern dude who lives in a world where evidence of a controversial subject is attainable, said subject is real,
yet denied by a very expressive number of people): President Donald Trump.
The scientific consensus on Climate Change is clear. And information is available to anyone with an internet connection. Despite that, Donald Trump, the leader of the modern world, doesn't believe it. And he damn well has access to shit we don't about this subject.
Donald Trump shouldn't be possible according to the laws of reality, then! Yet he is. He and MILLIONS more. And there is no "coverup", no "Church", no "Alucards", nothing trying to hide it. Please do tell me what better reason Donald Trump has than "denial" and "ignorance". Money? Manipulation? OK let's assume it, but what, then, are the reasons for his supporters (or even people who don't even support him, but believe the same)?
Then, after you explain how Donald Trump (and millions more, some of those being actually much smarter than him) can deny Climate Change, explain why Soma is unable to deny the supernatural with basis on the same terms, but on a world where there IS an actual effort to hide the information from him, and where evidence of it is hard to obtain by oneself.
I see your point, but I think you're overcomplicating a really simple issue: Humanity can be really dumb when it wants to. And by "really" I mean "really goddamn really". On the CV universe not only the supernatural is real, but certain groups of people do believe in certain "portions" of the supernatural world. But evidence? Nah, that's reserved for the top dogs only. On the CV universe, those who have access to this are those in on the Masquerade, more or less like our world's scientists have access to restricted shit we can only dream about.
PS: Most people will believe the supernatural with you giving them no evidence whatsoever. All you need is to cite the "right" supernatural claim for an individual to believe you. We live in an universe where there are real things with actual evidence that get denied, and impossible things with no evidence that get accepted. I don't see how that is so ludicrous on the CV universe when it's exactly how it goes on our world.
But how hard would it really be to take a good, unambiguous photo of a supernatural being in the CV universe?
It's not about how hard it is to produce evidence, but how hard it is to get people to look at it. And, depending how you were raised, THAT is really hard. I was raised in such a way that I won't even lose a single second with any claim of the supernatural that appears on my way. If Jesus himself produces fish to me, I will IMMEDIATELY discard the miracle as bollocks and go on my merry way to ignorance.
Even so, there will be people to believe it,
exactly like in the real world. Pareidolia itself gets people to believe in the most insane shit with zero effort. I evoke UMA News again to demonstrate that "believing evidence of the supernatural in the CV Universe" is not such a foreign concept in the CV universe as we're making it to be. However, not everyone will consider that to be trustworthy. I know I wouldn't.
We're discussing too many things at the same time, I think. There being evidence of the supernatural on the CV universe and people's ability to absorb this evidence are two separate, very different things. There being supernatural occurrences in this universe does not automatically make it implausible for people to not believe it. And, we have real occurences on the real world that get dismissed just as a skeptic would dismiss claims of a Skeleton moving via magic.