Warning: there is profanity in this clip. You probably don't have to watch it to understand my next points, so feel free to skip it if you wish.
The way I see it, the artists did gain a lot from the creation of their art. Their personal exploration probably did help them to reach a better understanding of their world. However, I do side with the established painter cohersed into juding that art show. It was the actual process and not the finished work that created that transformation, so the art itself said nothing because the context had passed.
All art is useful, but not all art is communicable. There is a difference between the act of making art and the finished work. Cultural art is something that should speak to observer. If it does not, then the conversation that should happen between masterpiece and observer is missing, and there is no enlightenment nor increased understanding.
Personal art needs only to speak to the artist. Under the right circumstances, a single line on a piece of paper can open the gate to passion, clarity, and wisdom--but it will only speak to that artist. It is the artist's conversation with the universe. Such a piece of work should rightly be treasured by the artist, but not necessarily enshrined for the rest of humanity. That would be telling people that this line has now been done, there is no need for more. Instead, the line should stay with the artist's heart and she should encourage others to find their own lines, to unlock their own passions and wisdom.
Which type of art is more valid? The very question itself is blasphemy in my opinion. Without cultural art, we lose our soul as a society. Without personal art, we can lose our very minds.
I must take a step back from my philosophical gushing and point out that even personal art needs to be shared to fulfill its purpose. In art therapy, this is known as "witnessing". Witnessing is when the artist shows the work to a supportive person, who lets the artist tell them what it means to them personally. There is no critique, no suggestions, just an act of listening to the sound of one person's soul being reveal.
At the same time, there is much to be gained by playing around with the art of others, as long as the original works are left physically untouched. It provides an interaction between the artwork and the audience, making the original piece more meaning ladened and important as the conversation continues. The following talk, though mostly meant to be humorous, is a prime example of entering into conversations with well-known artworks.
Granted, the conversations can become turbulent in some cases, but once you develop a personal relationship with a piece of work, it becomes alive and part of your mental fabric. Your brain now has a larger visual vocabulary to work with.
Here are a few sites online that will let you have your own conversation with art. Enjoy the process!