They are if you actively manage your relationships with an eye to maintaining redundant access to necessary materiel or having multi-pronged defense strategies. Singapore is constantly nurturing strategic defense ties with multiple allies and attempting to avoid existential reliance on any single ally. And the one nation they definitely wouldn't rely on is Malaysia, the country most likely to threaten their sovereignty. Ukraine's problem was they were politically too dysfunctional and dependent on Russia defense trade until Russia's successive invasions forced them to reform domestically. (To be fair, Russia had a hand in prolonging their dysfunction.)