I'm simply contrasting the level of fame Ross achieved, to his level of art. They are not equivalent at all. His paintings are of rather low quality.

I'm not saying Ross' painting is as bad as this extreme example, but to even a casual appreciator of world class art, Ross' paintings are of very amateurish quality. The stuff you'd see hung in a motel breakfast corner for example.

I've seen plenty of motel paintings, watched plenty of Bob Ross episodes, but the comparison doesn't seem fair. Motel paintings are often printed - you can tell by the CMYK dots if you come close enough. Ross at least seems to use actual oil paint on canvas supported by real solvents which seems a lot higher quality than the usual school process using acrylics or temperas. (Although granted using liquid white seems a bit dodgy).

So what is Ross missing. Not enough detail? Does not take enough time to paint a painting? Not enough paint on the canvas? Not photorealistic enough? Too photorealistic?

I would apply the uncanny valley dynamic to his landscape paintings. https://en.wikipedia.org/wiki/Uncanny_valley