Keep in mind that the Science Victory is also futuristic. We are no where near the ability to set off to Alpha Centauri. We've never even made it to Mars unless you count a probe.
It also is in the "future tech" era. That said, on multiplayer, it would be pretty annoying to fight against. Though I imagine the dev's felt a need to accelerate games which have taken so long to finish by conquest.
They could do something like idk stealth tanks or drones or special forces units or snipers (next level of ranged after bazookas). anything that might be based on our world just to keep it somewhat accurate. Like someone said I like Civ series because of how they are history based. I always imagined that a spaceship is just a slightly advanced rocket that could be built by 2050.