Evolution of tactics

Inverting the pyramid, prologue: a perfect tactic doesn't exist, because the efficacy of a tactic depends (on the players and) on the stage of football evolution.

Against: The only reason to assert that the efficacy of a tactic depends on the stage of football evolution is that we see that tactics have never stopped to evolve. But the main reason for this evolution is that implementing a new tactic needs years of practice. It also needs years of probable losses, so managers are pretty conservative in tactics, because they can't lose too many matches without being fired.