I might render the passage as:
The question of what makes something "art" is not a new one. Some artists today seem to have as their main purpose to mock art that can no longer be called "cutting edge" -- a label which is only a cliche. When art goes too far beyond the usual, people are puzzled or upset by it, and think that the artists have gone beyond proper limits. A similar public response, a mixture of contempt and confusion, has been a reaction to art for a long time, as far back as the age of Michelangelo. But the art that in the 16th Century provoked contempt and confusion as too original, would now be seen as old-fashioned, out-of-date, not original enough to provoke interest.
I have taken a few liberties with the rephrasing, but I think I have captured the sense of the quoted passage in somewhat simpler and less metaphoric language. The passage is not great writing. It does not focus on a single idea, but shifts its focus more than a single paragraph really should. It makes use of both cliche and jargon.
As to the specific terms asked about:
"contemporary" here means "of the current time" and "is hardly a contemporary one" simply means "is not new".
"gone too far" and "goes too far" are common fixed phrases, meaning that something has become improper by carrying a tenancy beyond a proper point. The idea of "going" in the phrase is usually metaphorical, it often means "has changed too much".
"failed to provoke" is a piece of art-criticism jargon, and here is technically grammatically incorrect as well. A piece of art is said to have "failed to provoke" when it is old-fashioned or unoriginal, and does not stimulate interest in the observer. This is an opinion, a judgement, phrased as if it were an objective fact.
"scratches its collective head" means that the general public ism puzzled or confused.
"furrows the collective brow" means that the general public is annoyed or angry or disgusted or showing contempt.
Both of these last two are taking stereotypical individual gestures showing emotion or attitude and applying them to a group. They could be thoguht of as personifying the general public as if it were a single collective person.