Dark Matter in totality is hard to disprove (as it's really not one theory, but a rather large set). But large parts of that parameter space is testable, and is

Dark Matter in totality is hard to disprove (as it's really not one theory, but a rather large set). But large parts of that parameter space is testable, and is tested. See WIMPs for example, where we searched extensively. Have we ruled out everything? No. But we have ruled out many variants, mass and coupling ranges.