The Barracuda class as an interim diesel-electric submarine

Were the Barracuda-class SSKs good diesel-electric submarines, and did nuclear attack submarines shorten their careers?

Yes: they were capable interim conventional boats, but nuclear submarines quickly displaced the mission they were built to cover.

The Barracuda-class SSK belongs to the transition between improved conventional submarines and the nuclear boats already approaching service. It was about as capable as a diesel-electric hunter-killer submarine of its period could be, but remained constrained by the limits of that propulsion type. Its short relevance therefore says more about the rapid arrival of nuclear submarines than about a uniquely bad design. A sound interim procurement can be overtaken quickly by a technological break.