I think the militia are just strange. If there are so many ships defending a planet, why is that planet not colonized?
Because bombing every new planet for 5 minutes is boring and not helpful for game speed.
It would be the same game as now, but early colonisation would take much longer.
think there is no immersion at all,
Actually, one could argue about that.
When a hostile EMPIRE owns the planet, its goverment will fight to the death, meaning you have to bomb them back into the stone age. They always have the hope that their mighty imperial fleet will show up and scatter the invaders.
A lone colonly however has no such hope. When their pity navy is destroyed, there is nothing left for them to defend their planet with. And they know for sure that nobody (that does not plan to invade them at least) will come to their aid.
So... what can they do? Try to make a stand? With what? Considering that all factions have no trouble whatsoever to nuke the living shit out of any planet they dont like, they cannot hope to stop the invading faction.
"Either you allow us to colonize your world or we will nuke your cities into dust". And in case you are wondering, no, if necessary we will wipe out the entire population. Your continued survival would be nice, but it is by no means necessary. We can colonize the planet all for us, too.
"And now, while our colony ships descends, we suggest that you choose your destiny.... and choose wisely"
Some Milita name also suggests that those are actually pirates..... so them being away may actually be better in some cases for the population.
And once the planet is colonized/conquered the population actually does have a certain interest in the victory of their current overlords. After all, the most likely cause of them going away is a hostile fleet nuking the planet from orbit. Not a prospect any planetary citizen does look forward too.
Last but not least, living under TEC rule is probably not the worst of fates..... you dont have to like their economic ways but on average you probably will have a good life. Although you could be drafted into military playing cannon fodder..... that obviously sucks, on the other hand the pay may be reasonable and we dont want to have hostile empires nuking our planet, we better help TEC to win the war. Or you could become a trade ship captain... getting very rich. One could also imagine at least a planetary democracy. It was never stated what form of goverment TEC or the Trade Order have, but then a totalitarian state rarely sees economic wealth like the Trade Order and would have probably failed to protect peace for that long. TEC clearly removes some of this due to emergency, but then every TEC citizen wants TEC to win the war for obvious reasons. And the Trade Order was likely incapable of helping on that front to much, it just wasnt designed with a fight of survival in mind.
Advent rule may be less entertaining but it is probably still acceptable and probably does beat marauding pirates in orbit. I mean, ok they are cybernetic enhanced fanatic humans with questionable motives and an unhealthy urge of revenge, but how much is your everday life affected by this? The little we know about the Advent leans more toward that membership in the unity, while encouraged, is voluntary. And if you dont have any psychic talents, you will be left mostly alone, as long as you dont cause trouble. The unity, while being powerful enough to force a limited numbers of individuals into submission, does not have the power to assimilate anything they want. Which even makes sense from a certain standpoint. The Unity seems to be a collective consciousness, it can have no interest in assimilating to many people who dont want to join the unity in the first place. Otherwise it would end up with a collective consciousness in which the majority of members want to leave..... that would not end well and the split of the Advent Rebels was probably pretty painful for all parties involved.
Vasari rule is probably the worst of all, they clearly have no concern of any kind about your well being. They will use slave labour, put nanites into your body, brutally crush any opposition by orbital bombardement and if you are unlucky they may just strip the planet right below your feet. Of course without evacuating you first, after all, space on ships is at a premium. So dont cherish to loud when they appear to be leaving..... the planets remaining lifetime may only be counted in hours.
On the bright side, you can be pretty sure that they will leave, after all they are on the run. With the war slowing down their progress, chances are good they will do so before entirely ruining your planet. On the not so bright side, whatever is chasing them is probably right behind their leaving fleet..... so your new freedom might be very short lived and result in your death. Considering that there is no record of any faction about the Vasari Terror, it seems quite likely that a former Vasari colony, or any colony for that matter will be destroyed without mercy by that terror. However that would be the fate of any world not evacuated then, it seems unlikely that TEC or Advent could stand against the ancient terror that wiped out the once vast Vasari Empire. That leaves only running, like the Vasari Rebels suggest.