Even in the Kotor CG it says as much, the Navy really being the only good thing and even then the Navy is kinda...meh compared to other eras. The Army is just a bunch of planetary militia's/merc groups and having no real unified commander until Revan, until he came it was mostly the Defense Ministry and the Navy commanding the ground troops...which is really terrible.
The pay and conditions are pretty terrible too.
In terms of prosperity, it's probably either the first three quarters or so of the post-Ruusan Republic, or some random time period of prolonged peace/no sith wars.
In martial strength, it's obviously the height of the Clone Wars.
In terms of the Jedi, it's explicitly the Prequel Trilogy/the height of the Clone Wars.