The main reason of the Kilratihi ships beeing inferior to terran counterparts is different philosophy and sotial structure of the cats. Darket and Dralthi fighters may ni inferior to their human counterparts but are much faster and cheaper to build, wich means the Empire can throw much mor of them. Theye are flown mostly by non-nobilyty, wich mean that their pilot's lives are worthless for their nobile superiors. Also, kilrathi mature much faster than humans, wich means the replacments are also faster. If you compare the havier fighters, flown mainly, if not exclusively by nobility, you'll find that they are equall or even superior to their confed counterparts (i.e. Vaktoth have weaker shields than T-bolt, but is more manouvreble, a bit faster iirc and carry more missiles, while having equal gunpower, and Pakthan is also superior to longbow in any aspect but shielding).
In Saga prologue the fighters you face are either light and chep darkets and dralthis, Gothris wich are not-so-new or zarthos wich are electronic warfare ships and tot really combat fighters.
Technologicaly speaking, most innovations during the war were kilrathi developed (cloaking, torpesoes, particle cannonnos, etc) so you cant say cats are technologically inferior to humans