The slow rate of technological advances might have something to do with the damage that the Republic suffered in the New Sith Wars, looking at the Republic Dark Age and the condition of the Army of Light by the Ruusan campaign. It took centuries for the Republic to recover from that war.
Even so, the pre-Clone Wars Republic had at least evolved centuries ahead of the KOTOR-era Republic:
1. Droids in non-military fields had gotten better (more intelligent) and produced in a larger scale.
2. Speeder bikes and swoops of relatively the same size had been made, and podracing had been established and became a popular sport on many worlds.
3. Medical technology had clearly evolved, with disease becoming a rarity on civilized, developed worlds like Coruscant. Epidemics only occured on isolated worlds such as Jabiim.
One thing that has to be taken into account is technology is harder to spread and update on a galactic scale than a global/planetary scale, especially in a intersellar society with millions of different sentient species, which is one of the reasons why most technological advances are shown in military applications.