I'm sure this will counter many points but let me throw a few ideas/opinions in here too.
1; technology. The whole point of Sci fi is the rule of cool and what's more important than a giant beam saber wielding mecha with particle beam weapon turrets on its shoulders. (well not for all but you get it). The idea should be to follow cool but keep a balance. Technology should be moderately described or a rough guideline, say, "think star trek".
Find a balance of a weapon and let someones technobabble be fluff.
2; military op, Mary sue etc etc. Alright, some of my more successful nrps have occurred because one or more, (usually me, not taking credit for win but just being honest.) being a tad or overly op. It's called an antagonist. If everyone starts on equal footing, then its just another typical, plain age of empires roleplay game where we all start in the space age. Just, blah.
You need the lack of general balance to encourage struggle. People don't care for slice of life, they want fear and paranoia, that shit could go south quick. All this said, people would need to agree on some basic things. What is considered op. Star trek for example. The Borg are imho pretty damn op. (unless you have picards or janeways.) but in your RP would that race be too op? Would too op be a romulan empire on hgh? Not exceptionally more technologically advanced but far greater in number and experience?
That's where you, the GM has to decide. Just have some faith, let some people be smaller nations that are bound into a bloc like the EU and the antagonist be your Russia. I'll be more than happy to show you how it can work.
3; points system. No.
Points are the first step away from a narrative towards a stat base. I'm sorry but people like myself are in it for the story, not to use math for making my nation, regardless of how rudimentary it may be.
4; absurdly long ns's. I totally agree. People skip to military every time. They'll look at characters when relevant and history only if they are intertwined. But seriously, 3/4 skip right to the military.
5; have an overall story to give a boost. The whole everyone was once in a massive star empire thing is overplayed, ill give clocktowerechoes that, but maybe one of the bigger nations starts the RP at odds with another major nation, forcing those nearby to react. Even if they aren't directly in the warpath, what would tip the balance more than a nation near nation B, who fears nation A, announcing it is siding with nation A. Now B is in a pickle, facing a strong force from A, but now having a small nation that albeit couldn't win in a major war, still be a real concern.
Gotta make some sort of overreaching story that can affect everyone or its boring first contact stories over and over.
Feel free to agree/disagree as all prior posts points are fair and respectable, but these are the major points I can think of.
Edit,
Oh and 6; Have fun and don't be butthurt if your nation loses. It shouldn't even be a loss, it should be a new story arc about the oppression of your people, the forcing of a new government and the shit storm that follows. Look at Iraq. More drama exists today than before the second Iraq war. And drama is king.