After looking into this a bit, I can say that I don't subscribe to positivism or relativism, even if they are trendy in philosophy class these days. Both seem to reject realism and promote groupthink.
"Can we not account for both science's existence and its success in terms of evolution from the community's state of knowledge at any given time? Does it really help to imagine that there is some one full, objective, true account of nature and that the proper measure of scientific achievement is the extent to which it brings us closer to that ultimate goal?" (The Structure of Scientific Revolutions, p. 171)
I have not been publishing in many years so my reading appetite has diminished, but I think the trendy -ism in philosophy of science is not so much relativism but pluralism.
Regarding your quotation, Feyerabend explicitly rejects that science is successful and in fact has been actually harmful in understanding in the case of biology. And he argued cogently that "science" should be seperated from the state with as much rigor as "religion" is. He was one of the greatest anarchist minds I ever had the pleasure of meeting.
Nancy Cartwright makes a similar argument but keeping a realist stance about how science doesn't really make progress describing the fundamental truths about the world. That is, people usually hold up the wonders of the modern world as evidence that science progresses towards universal knowledge, e.g., jets fly! But she would say I think that jet engines do not depend at all on scientific understanding of turbulence, which tend to be completely wrong in the material world, and require all kinds of simplifications and specializations in order to make this concrete jet engine work. [0]
"Can we not account for both science's existence and its success in terms of evolution from the community's state of knowledge at any given time? Does it really help to imagine that there is some one full, objective, true account of nature and that the proper measure of scientific achievement is the extent to which it brings us closer to that ultimate goal?" (The Structure of Scientific Revolutions, p. 171)
I'll have to check out Larry Laudan, thanks.