To me, lots of 20th century art 'developments' really seem to boil down to using pseudo-visual-philosophy to justify laziness about technique. I think it's cool that we've arrived at a place where it's ok to put cool chapes on a wall and enjoy it! Rothko's color fields are good cool shapes. But these same developments meant the art schools my teachers went to did not teach them strong fundamentals that were considered par for earlier generations. Acquiring the skills my soul aches for has been infinitely harder than it should have been.
Additionally, painters who work like Rothko are truly expressing so very little. It requires mental gymnastics to see it as something other than wildly derivative and barely expressive. The art is no longer the piece but the required-reading artist statement. I know a lot of people who love this kind of stuff, all the intellectualism about it. Good for them. But I think this type of 'art' has reached its peak and young people now want paintings that explain themselves. Rule of thumb: if reading something or receiving an explanation is necessary to appreciate a painting, it kinda sucks.
There are some people who actually think we should just make Rembrandts again, and I agree it's boring. But understanding how he made those paintings so we can learn and apply those skills to make new paintings that we want to make, to express things about what we experience in our lives that's actually exciting. And the establishment art-thought is that this isn't art anymore, painting things you see is 'low' and unoriginal. I couldn't care less about being an 'artist'. I just like making paintings and looking at paintings. And the ones that conceptually pat themselves on the back for not being very good paintings are typically very uninteresting to look at.