I think you and share all of the same premises about art, and I'd love to get a drink and have a conversation... But: Please don't use Rothko as a negative example! Have you seen any Rothko pieces in person? They are by no means solid blocks of color (though some do look it in reproduction), and they grab my attention immediately. Like, they dominate any room they're in, and pull me back towards them over and over again. It's hard to articulate, but there's something both stimulating and restful about his canvases. Especially after walking through a gallery, or a city, where my visual senses can get overloaded, standing in front of a Rothko is like an immensely welcome psychic reset. I used to walk across the bridge to the Tate Modern specifically to go stand in the Rothko room for a while.
I realize that's all subjective taste, but I'm hardly the only person who reacts to him that way. You're right that lots of people assumed the secret was "hey, it's just large blocks of color", but none of his imitators produce anything like his effect on me. There's something else going on with his work.
I used Rothko as an example of a famous and in my opinion highly underrated artist that those who "hate art" love to use an example of "bad art" because "anyone could just do that". Of course his pieces are breathtaking and once you're aware of the process of how they're created it changes them forever for you.
I realize that's all subjective taste, but I'm hardly the only person who reacts to him that way. You're right that lots of people assumed the secret was "hey, it's just large blocks of color", but none of his imitators produce anything like his effect on me. There's something else going on with his work.