The harder question is the one about art that does not require skill.
It's all in how you define skill. When it came to my past work, when teaching children to understand and appreciate various forms of creative expression, I follow the
theory of multiple intelligences. Within this frame work, you can look at an artist, say an untrained actor who is incredibly skilled at interpreting and eliciting emotions and appreciate that they have strong skill in interpersonal and intrapersonal intelligences, while maybe they lack in other areas. If they lack in other areas, if they have a capacity, an artist can work on building their intelligences in other areas, but no matter how much he studied, I doubt Mikhal Baryshnikov could become a math genius. I guess this is why I defend Rothko so vehemently. He has strong intrapersonal and visual-spatial intelligence. If you measure a painter's skill by the kinesthetic skill to be able to control a brush, and say produce a photo-realistic image, then Van Gogh would be considered a failure - he himself in his earlier career was constantly frustrated by his inability to control the brush, and was driven out of more than one art school and condemned as a failure because of it, until he decided to move away from attempting to recreate an image and instead to paint the underlying emotion of the image.
Which image of night do you prefer?

One is "Edge of Night - Timber Wolves" by Robert Bateman," who is known as a virtuoso of the kinesthestic skill of brush control and naturalistic intelligence related to a strong understanding of biology, botany, etc., while the other is Van Gogh's "Starry Night." It's clear who has the stronger brush control of these two artists, and I think, also clear who has the stronger grasp of emotional expression.
When it comes to appreciating art, it's a personal experience, very much about which areas of intelligence stimulate you and which you value most. Just because an artist lacks a skill you value most doesn't necessarily make them unskilled. People can deeply value a Rothko painting because they hold values different from your own. This doesn't mean your values or theirs are wrong, just different. It's what makes art so interesting and controversial.