It seems possible to argue for many policies from either perspective. For example, you could argue against war from a left perspective by calling it imperialism and full of human rights violations. But you could also argue against war from a right perspective by pointing out how the military-industrial complex takes advantage of a large government to milk the populace for cash. Or with the covid relief bill, left-wing supporters may want to put most funds into direct deposits to average citizens because that seems to directly help people. Right-wing supporters may argue for the same thing because a large, complex system deciding who gets relief is vulnerable to lobbying and litigation effectively siphoning that relief to the highest bidder. So how is it decided if a policy is left or right?
These are just examples, I am interested in the subject in general. I have seen other questions asking about how left and right people are defined, but I don't think this is a duplicate as it is about policy.