The problem with the sentence as written is the phrase "considered to be," which is in present tense. From context, we know that Schubert was considered to be lightweight, but the tense doesn't reflect that. This eliminates (A), and calls (C) into question as well.

Choice (B) is not a complete sentence; there is no central verb. (D)'s construction "had considered" is in the past perfect tense, which requires that there be a clear "past" that the past perfect preceded. There is no clear past--the tense in "reflects contemporary thinking" is present, as is often the case when discussing art or artifacts. That leaves (E), which avoids all of these errors, and is correct.