I like that you've taken to heart how dangerously weak "many" is on Strengthen/Weaken questions.
However, for the sake of Reading Comp, it's normally more important to just think about the central ideas in the passage, as THEY are primarily what are being tested.
The reason (B) is correct is it goes against the passage. (A), (D), and (E) go with the passage. (C) also goes against the passage, but goes against a small detail, while (B) goes against the central idea.
Why didn't critics appreciate Davis?
The last paragraph says it's because they "feared his broadening of possibilities". He kept reinventing himself, breaking his own mold.
So (B) is simply going against the central idea of the last paragraph by saying, "Not so, author, many critics greatly ADMIRE that kinda behavior".
=== other answers ===
(A) This is consistent with the passage. The author mentioned that improvisation is valued.
(C) This is pretty tempting. Lines 32-34 suggest that jazz purists were not fans of using electric vs. acoustic piano. So this answer seems to go against that. Ultimately, though, this line is specifically about Herbie Hancock switching from acoustic piano to electric piano. Meanwhile, (B) addresses the final paragraph, which is concerned with why critics didn't like Davis as much as they should have. So (B) is much more relevant to undermining the author's explanation of how critics regard Davis.
(D) This is consistent with the passage. The author suggests that Miles Davis, because he had a long career, had more time to reinvent himself, which is ultimately what critics didn't like.
(E) The distinction between musicality and virtuosity isn't made in the passage, so this wouldn't go against anything the author said.
Hope this helps.