Audiophiles, it is said, use your music to listen to their gear. It is well established that most of what audiophiles "hear" is subjective -- in blind testing, they cannot tell the difference between their solid gold cables, and cheap cables from Walmart. This doesn't mean, though, that they're not hearing something.
Hearing, like vision, is a construct of the mind. Just because we have to know some related fact before we can "hear" or "see" something doesn't mean we're not hearing or seeing it. The tricky bit is that you can tell an audiophile that the solid gold cables with the directional arrow on them are in use, and, whether they are or not, the audiophile will hear the more three-dimensional sound stage, or whatever.
There are, assuredly, things we can see in photographs that are not there. Photographs taken with a Nikon D800 and a Zeiss Otus Mumblefart lens (or, more to the point, with EXIF data which suggests this) appear on the internet, scaled down to 1500 pixels on the long side, and people will exclaim with delight. Shoot something with a cell phone, make sure the blacks are dark, and tell people you shot it on film, watch the cooing begin.
In short, people see stuff they think they ought to see based on what we tell them. Stuff that is not there.
On the flip side, "serious photographers" are fond of rattling on about "the light! the light!" which usually means either waiting for sundown, or using a really big modifier. Then they take a picture, and show it to people. If you tell your audience about how amazing the light was, they'll see it, most likely. If you don't, they'll see that you shot it at around sundown, and totally miss how "awesome the light is". That's because there isn't anything awesome about the light. It's sundown. Happens every single day. Also, we've all seen a zillion of these things. Ho hum.
In general, self-styled photographers spend a lot of time monkeying around with things that non-photographers won't see unless they're told about them. This is OK, because mostly self-styled photographers are shooting pictures for other photographers to look at, and those people will quite likely notice that you used short lighting on the plump subject, and will applaud approvingly.
Well, there's a lot of technical stuff that we won't consciously notice without foreknowledge. Either we get told about the Zeiss Zebulon lens, or we just know short lighting, or whatever. Without the knowledge, the technical feature is invisible. Either because it does not exist in any measureable way, or because we're blind to it.
There are technical things which do exist, in a measurable way, to which we are blind, but which may nonetheless change how we perceive the picture.
Try this experiment. Gather up some photos. Sort them in to pictures you think are "good" and pictures you think are "not as good". Now look at any real resource on composition, by which I mean, avoid resources aimed at photographers. Take the ideas and principles you learn, and apply them to the pictures.
I bet you'll find that the "good" ones tend to align with the ideas and principles better than the "bad" ones.
Ugh, so now we're got a mess.
There's stuff that's measurable (real) and stuff that's not measureable (not real).
There's stuff we perceive consciously. There's stuff we perceive, but not consciously. And there's stuff we're completely blind to.
So, to summarize:
There are things we perceive consciously. These may or may not be real.
There are things we perceive unconsciously. These tend to be real, but there's probably some sort of continuum of consciousness, and of realness.
There are things we're blind to. These may or may not be real.
The magic is probably in the stuff we perceive unconsciously, which is mostly real stuff. If just anyone can perceive it consciously, they can probably just shoot it themselves. It's "obvious".
If most people are blind some stuff, who cares about that stuff?
If most people can feel something, but only unconsciously, well, now we've got something, don't we? This is the sort of thing that actual theories of composition are getting at.
If you don't know to look for it, you won't particularly notice that the most interesting thing in the frame (the "subject") is also the highest contrast point. You won't notice the way things are specifically organized by contrast, by position, into a heirarchy of importance. You won't notice the way complementary colors are used.
But these things will most likely affect you, you will mostly likely think the picture is "better" for them.