War breeds innovation, however. Weapons advance at a slower pace when there is no need for for them to advance, just like everything else. In a war, however, the pressure is on, so to speak.
Consider the advancements made during World War 2: in 1939, all the major combatants still had biplanes in their arsenal; in some cases those biplanes composed a major part of their fighter force. (The Gloster Gladiator and its Italian equivalent.)
By 1945, two of them had jet fighters in operational service, and two more would have had jet fighters in operational service by 1946.
Conversely, though, when your weapons are demonstrably superior to those of everyone else, you don't feel the need to advance them. Germany's armored forces had much the same equipment from the blitzkrieg in Poland until El Alamein. It wasn't until German Panzer IIIs and IVs ran into Russian KV-1 tanks that work on the Tiger began, because until then the III/IV had been sufficent to deal with enemy tanks. The KV-1, however, was impervious to their 50mm and snub-nosed 75mm cannon, and clearly something better was needed. The Panther was a direct response to the Russian T-34.
And getting new weapons into service takes time. The weapon that first put you in a posistion to really make a fight of it with the Shivans in FS1, the Avenger, was already nearing the completion of its development before the Shivans came. The same goes for shields (the MX-50's tech description describes one shields experiment, and seems to imply others). The same must hold true for the Medusa bomber and Tsunami bomb. I would guess that all the ships and weapons you use in FS1 were either pre-exsisting or already in development, with the exceptions of the Ulysses, the Ursa, and the Banshee.
