Why Canada's Tribals were near the end of useful service by the 1960s

Could Canada's Tribal-class destroyers have been modernized for service beyond the 1960s?

Possibly for a navy with gentler requirements, but Canadian ships were already heavily worn after more than twenty years of demanding service.

Canadian Tribal careers extended from Haida's retirement in 1964 through Athabaskan's in 1969. By then the ships had served for roughly two decades and had already absorbed demanding wartime and Korean War use. A less demanding navy might still have extracted useful service from them, but their condition made further Canadian modernization unattractive. The class remained capable even though these individual hulls had reached the end of hard operational lives.