Peer review as currently done certainly isn't foundational to the scientific method, but the general principle of having ideas checked and examined by as many other minds as are capable of understanding them, does lead to stronger and more reliable ideas over time. Not everything that science deals with is quantifiable or directly testable; results must be interpreted, and theories have to be made about the wider reasons for those results in order to come up with the next set of experiments; this is the realm of discussion and argument, rather than measurement or direct tests, and science is best advanced when there is strong, productive discussion among competent arguers.