The Soyuz-class was too old for service 40 years before this game. It's a Tier 5 Constitution situation - There's only so much you can do with a ship before it's just too old. And the Light Cruisers, primarily the Miranda, were old when the Constellation-class was new, and you don't ever see Constellations.
It's just too old, especially for a T3 or T4 ship.
People still use that "too old for service" argument? Even after the T5 B'Rel, the T5 T'kyr and the T5 Excelsior?