So, I want to talk about those two factions and their destiny.
By the time of the Beast War the Republic's fleet was one of, if not the, most advanced force in the galaxy.
This saying is the one that I want to deny. Being correct, not to deny but to prove, that in that time, the taiidani fleet was already one of the most advanced fleets in Universe.
Yes, it was told by the Cata manual, that
WIth a few years of planning time, the Republic has stopped trying to match the Imperialist factions on a gun-to-gun basis, and are now trying to seize the high ground by using advanced technologies. The Taidani military invested vast amounts of their financial reserves in manpower, for a few crucial fleet Research Stations. Their hope was of making ship design and weapon breakthoughs that would allow them to defend the Republic's borders with a vastly reduced fleet.
With what to begin... Ok, let's start.
First, if you look at the homeworld 2 fleet, then you can see, that there is no extra technologies, that could be identified as "advanced" - nor hiigarians, nor vaygr. Defence Field Frigate? I guess, it was seen at somtaaw sentinel force field, and before it taiidans already got their DFF. Big Cruisers (taiidani heavy cruiser = HW2 era heavy destroyer)? So what? Simply there was no need of these ships, as at the time of HW & HWC taiidani fleet was the best one. Only when it came for vaygrs to defeat the taiidans they made their b-cruiser against all the capital ship of the taiidani (all the types of the destroyers - light, missiles, heavy...), and then hiigarians made their b-cruiser as the simetrical answer to the vaygr thing...
Little remark: if we look at the vaygr fleet, we can see that they are better made for destroying big ships, destros, cruisers; hiigarian do better work with sneaky frigates, they also has so much frigates to work with strike craft. So you can understand what enemy was facing each race. The same goes with the HWC - somtaaw got little fleet that did not intended to fight with capital ships. At least without some kushan destroyer/cruiser. And talking about kushans - they were just the copy of the taii fleet and shared the same tactics.
What happend to kushans in HWC? - they kept the same fleet for 15 years to keep fighting with taii imperialists. The 4th attack of Imperialists was the last as they were on the edge of there economics possibilities to make more fleets - they even tried to search for help with Turanics and the Beast! These really were the last days of Imperialist glory.
We need to understand that in HW space there is no extra-cheating tech that can easily vaporise the enemies. To defend yourself from the frigates you need the destroyers (of course, you can have strike craft, but this ain't reducing people using and is not making your fleet more mobile, as they don't have hyperdrive for the vast spaces), to defend from the heavy cruiser... yes! Taiidani Republicans made their own Death Star, oops, Nomad Moon! And that's all - what the point to change system that works well?..
So, about the resources... After the revolution TR go 60 world of 150, TI - not so much, I think. As HWC writes about carriers:
At the Empire's fall there were 137 Saarkin Cho on active duty, and by the time the ashes of the civil war cooled approximately 70 of these heavy Carriers were still active, 19 of these flying the colors of the Imperialist faction.
That means, that TR got 50 of working stuff, which was working for one army. And about 20 carriers worked for the disunited imperialists. TR got 60 world, with big factories, supported by a system, a little bit broken as some the parts of the Empire was absent, but still working, with ability to produce ships of the famous taiidani fleet; and on the other hand - divide imperialists worlds that had no potential alone. (compare to the Russia and post-soviet republics, where factories were abandoned as the system feeding them broke)
So, you can see that TR made advancements but have put it into the big objects, and on the other hand they had no big need of general strategy rethink (of course, they didn't know that Makaan would come...) as there were no such enemy, so they could use the old strategy fleet further. And you know, there is no need in hull change if it works well - just change the parts inside )))
And the last thing - beliefs that Imperials got all the fleet in their hands, and then the Republicans were fighting on some civilships ))) As you refer to any civil war, any army consists of a man, and they would choose their side too. The reds and whites in russian civil war (1917), american civil war... Especially if we remember that there was already rebellions - cpt. Elson, for example... So I think that Taii civil war was so hard as all got their part of the Imperial fleet.
P.S.: And if each less or more advanced imperialist solar system is capable of building a personal h.cruiser, then TR must be capable to build them "like causage" (c) Khrustchev