There was an interesting documentary by broadcaster Muriel Gray on some of the extremes of modern art. One exhibit was an "installation" consisting of rotting animal organs hung up in a room. Muriel was clearly retching at one point. It later emerged that the whole programme, including the "art" was in fact a clever parody.
Now if (some) modern art is indistinguishable from a parody, what does that say about its worth? Or perhaps the parody is itself legitimate art in its own right. To be fair, I can accept self parody or things that "challenge the nature of art" or whatever as (potentially) having some merit and / or legitimacy, but once most of it seems to have degenerated into self parody, or "what's the silliest thing we can get away with" I'm inclined to be cynical.
Simply claiming something as being "art" doesn't preclude pretentious rubbish from being an actual thing.
Now that said, I personally like and see value in Jackson Pollack's work, but don't get Rothko at all. I'm reluctant to dismiss Rothko, however tempting, as he is valued by people I respect. In particular there's an amazing piece of "modern" music ( as my wife says "pling plong music") by Morton Feldman inspired by the paintings in the Rothko Chapel. Feldman's music might not be regarded by everyone either but I find it amazing. Clearly the paintings meant something profound to Feldman, so I can't really dismiss them.
View: https://youtu.be/1ZZ0DYIkaP8?feature=shared