Everything is looking good... I've got a nice starting system and, as soon as the Argosy gets out of the dock in two turns, I have a juicy system lined up that's close to my homeworld and has good resources. What the heck is THAT? Oh for Pete's sake... the Horatio put an outpost in that system! Ok... this can be fixed. There's a Savannah planet in there and I can research Savannah Colonization before that outpost becomes a colony. Cool! I can snatch that system from Horatio because the Vaulters build colonies immediately and don't have to wait for an outpost to develop. Mwahahahaha! I'll just putt-putt around for a few turns until that research is done.

Ok, here we go... wait... what the hell is this? I can't colonize because the system is already colonized? Ummmm... it's NOT colonized, there's only an outpost here. You mean, the Vaulters can't contest a system that has an outpost in it? But ALL the factions can do that! Well... game over... it's turn 18, the Horatio have just parked their butts really close to my home system, and there isn't ANY decent candidate for a 2nd colony in the vicinity. This needs to be fixed or my first game with the Vaulters will be my last.

It's intentional cause all other factions have a mechanic that isn't instant colonization, Vodyani can't dock their ark with someone who has an outpost. I'm unsure if Unfallen can colonize someone who has an outpost, but it'd make sense given they're limited to adjacent systems. Vaulters on the other hand has the faster colonization ship around and while it takes a bit for them to colonize again, it's instant and they get bonuses, and they got portals to remedy long distances.

Apart from that, fgalkin said the rest! I'd recommend try a new playthrough, scout at the start and when you settle, make a new ship design with only engines and use one or two of them to scout far reaches of the galaxy while probing too, find a great second and possible third system, and don't worry about distance the portals fixes that. c: