It's not the most optimistic. With the full lore you very much get the sense that Union, the Federation essentially, has allowed elements of liberalism and opportunism to creep in on the periphery of its power for expedience. Union makes deals with incredibly corrupt feudal societies and borderline genocidal corpo-states, and may have committed a time-dilation exacerbated preemptive extinction attack against a distant human civilization before the development of FTL tech (the appropriately titled PISTON-1: KINETIC TOTAL BIOME KILL) during its brief fascist takeover. Because of said time dilation and the extreme distances, the attack is still technically in progress and very difficult to stop; when the other civilization detected it, they were rightly very unhappy with Union even if Union's current iteration is trying to stop it. Then there's what happened to the only nonhuman civilization ever discovered, unfortunately it was during the aforementioned fascist phase of Union.
The game has dark elements, and terrible atrocities were perpetrated by Union in the past, the optimistic part is where the players come in. Missions often involve siding with labor revolts, freeing enslaved worlds, et cetera. Union and the galaxy at large are flawed but can be changed for the better. By application of incredible violence and mecha magic.
I always found HORUS or Ungratefuls based campaigns much more compelling than Union for these reasons.