Skoyles's third argument is that 'realizing that ideas compete with each other is essential if we are to see why criticism matters in science.' By implication, if we suppose that ideas do not compete, then no sensible account can be given of criticism mattering in science. O.K. So I have to explain why criticism matters in a world where ideas do not compete.
I start by assuming that everybody's imaginations are limited and fallible, scientists' included. Progress in science requires imagination. On Popper's account, imagination may come into play in seeing something as problematic which everybody before had taken for granted, or in seeing a possible solution to a problem everybody before had been stumped by. But one can be mistaken about what is really problematic or one can be mistaken about the correct solution to a problem. Criticism amounts to providing a reason, whether grounded in a fresh thought or in a fresh experience, for thinking one's conjecture possibly mistaken. Of course, one can think one's conjecture mistaken without having any reason to, beyond an appropriately modest belief in one's own fallibility. Criticism provides a specific reason to do so, and may, at the same time, suggest to one the way in which one might be wrong and the way to go to improve the conjecture.
All this is true in philosophy or literary appreciation or theology as much as in science. The difference in science is that criticism is often grounded in matters of public experience, or at least of repeatable experiments, so that it is much easier to come to agreement with colleagues in the field that a conjecture was wrong and in need of remedy or replacement. In none of this are ideas active. People come up with conjectures and phrase them in a way that helps others have ideas with a similar logical content. People think up alternative critical ideas and voice them with a similar intent at communication, or do experiments that lead them to think the original conjecture in error, and publish their results in a manner designed to provoke their colleagues' understanding.