The opposition between realism and idealism is one of the many ways in which philosophical myth building leas on astray.
There's just the world, and included in it are our reactions to it. — Banno
I don’t think Karl Popper would agree with you here. He was heavily influenced by Kant in his philosophy of science. He would want to say that the influence of Kantian idealism on notions of the relation between the subject and the world led to a change from naive or metaphysical realism to forms of positivism.
Beyond Popper and Kant , phenomenology recognized that pointing to a world out there that we simply react to is an incoherent way of thinking. Each change in our account of this world carved up its particulars differently.
One of my favorite quotes on the relation between subject and object:
“Knowledge is taken to consist in a faithful mirroring of a mind-independent reality. It is taken to be of a reality which exists independently of that knowledge, and indeed independently of any thought and experience (Williams 2005, 48). If we want to know true reality, we should aim at describing the way the world is, not just independently of its being believed to be that way, but independently of all the ways in which it happens to present itself to us human beings. An absolute conception would be a dehumanized conception, a conception from which all traces of ourselves had been removed. Nothing would remain that would indicate whose conception it is, how those who form or possess that conception experience the world, and when or where they find themselves in it. It would be as impersonal, impartial, and objective a picture of the world as we could possibly achieve (Stroud 2000, 30). How are we supposed to reach this conception? Metaphysical realism assumes that everyday experience combines subjective and objective features and that we can reach an objective picture of what the world is really like by stripping away the subjective. It consequently argues that there is a clear distinction to be drawn between the properties things have “in themselves” and the properties which are “projected by us”. Whereas the world of appearance, the world as it is for us in daily life, combines subjective and objective features, science captures the objective world, the world as it is in itself. But to think that science can provide us with an absolute description of reality, that is, a description from a view from nowhere; to think that science is the only road to metaphysical truth, and that science simply mirrors the way in which Nature classifies itself, is – according to Putnam – illusory. It is an illusion to think that the notions of “object” or “reality” or “world” have any sense outside of and independently of our conceptual schemes (Putnam 1992, 120). Putnam is not denying that there are “external facts”; he even thinks that we can say what they are; but as he writes, “what we cannot say – because it makes no sense – is what the facts are independent of all conceptual choices” (Putnam 1987, 33). We cannot hold all our current beliefs about the world up against the world and somehow measure the degree of correspondence between the two. It is, in other words, nonsensical to suggest that we should try to peel our perceptions and beliefs off the world, as it were, in order to compare them in some direct way with what they are about (Stroud 2000, 27). This is not to say that our conceptual schemes create the world, but as Putnam writes, they don't just mirror it either (Putnam 1978, 1). Ultimately, what we call “reality” is so deeply suffused with mind- and language-dependent structures that it is altogether impossible to make a neat distinction between those parts of our beliefs that reflect the world “in itself” and those parts of our beliefs that simply express “our conceptual contribution.” The very idea that our cognition should be nothing but a re-presentation of something mind-independent consequently has to be abandoned (Putnam 1990, 28, 1981, 54, 1987, 77)
Dam Zahavi on Putnam