“oh, well, it’s projection of 3d on 2d and it follows such math” or “one of the main reasons why brain thinks something is beautiful is symmetry”
Though true, these seem like kinda dumb things to say about a painting? “Look at this picture!” “Ah yes, pictures, projections of 3D space onto a 2D plane” misses 99% of the point. Note that these are more useful if you are trying to create a painting, or analyzing the technical details of the painting (e.g. “wow what good linear perspective!” or “ah, that’s how you draw a icosahedron” or “ah, perhaps these kinds of symmetry are a good way to make pretty things”)
“as rationalist I for a long time thought that we need make pictures more useful, for example not put them into museams, but draw on wall everywhere, because currently walls are either plain or have ornaments of very low artistic quality”
Likewise, this is mostly not about the painting, unless you are currently planning to buy the painting and hang it on a wall.
It’s a warning against making your identity big.
Let’s take your example’