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
I’d say he certainly was an artist. If he was a good artist or not is a matter of opinion. Certainly from a technical and conceptual point of view there’s good argument he wasn’t exceptional. But certainly his work, or the labor of his work, has been appreciated by many.
How do you become an artist? Make art and say you are an artist. How do you become a professional artist? Have someone pay you to make art. I'd say he qualifies.
Maybe not professional artists where we get paid to partake in our creative outlets.
On the other hand, Vincent Van Gogh only sold a single painting in his lifetime.
Bob Ross was more professional artist than most. He is still widely known for his work teaching people how to create new creative works.
Bob Ross was a wonderful figure who democratized the act of painting to the mass consumer demographic. The level of fame he attained is much higher than the quality of his paintings.