It basically shows how silly and under-developed the Galactic War currently is. They need to add in more depth, maybe indicating certain tech levels of a system, so that we can build up our tech before entering into an unwinnable battle.
Yeah, I've had to use hundreds of Astrae before. half with engineers which immediately build anti orbital and anti-air defences because I had bots and teir 2 vehicles and no air/t1 vehicles. It can be hard, but it is doable
As well, you could use 20 empty astraei to scout for enemy commander, then if you have vanguards or at least infernos you can try to drop 20 of them. If 1-5 land around the commander, they will score the kill.
You don't clear all other systems first. That is for that "bosses" where you play against 2-3 AIs. Normal multiplanet systems against 1 AI, kill em before they escape planet. Or clear all single planet systems first and pray for orbital tech and superweapons. And yes galactic war is unfinished piece of ####.
My strategy of choice was to drop 10-30 units, some of them being builders and most of the rest - AA-tanks without any AA it's REALLY hard to drop anything), quickly build teleporter and several AA-towers and connect teleporter as soon as it's build (units on my base are already swarmed into other end). Without orbital tech Astraeus is the only allowed unit, and AI usually spams his planet with tons of air, that's why so much AA is a must. It smells like a hugely unfinished part of the game, but it had it's pluses - I'm now used to carefully placing and ROTATING teleporters, thing that I've never really seen any player doing in replays/streams, which usually leads to their units being stuck and bottlenecked in some landscape parts or forced to go a long way to the enemy.