Hi Haley,
The reason that the answer to this question is (E) and not (D) is that the author is making the argument that "the forward looking quality attributed to these artists should instead be credited to their exceptional aesthetic innovations rather than to any power to make clever guesses about political or social trends." The author is saying that we should look at the quality of their art and not to how closely they were able to predict social and political change.
(D) is incorrect because the author only talks about adjusting to social conditions in the very last paragraph about Delacroix. This example is given in contrast with the other visionary artists mentioned who were supposedly anticipating social change before it happened. The author doesn't ever say that one is better (more valuable) than the other.
What the author does describe as important is the quality and aesthetic of the artwork.
Also, just a side note: In a case like this where you are looking for something the author thinks, an incorrect answer choice may contain information that is not in the passage. It doesn't have to directly contradict the passage, and you may not always be able to point to a specific place to rule it out. Sometimes it will be enough to say that the information wasn't in the passage, so we don't know that it is true.