Well, after finishing game there is just bunch of stuff i kinda dont get:

1) How long actually taken this expedition? Its is clearly stated by JULIA that Rachel is awaken after 60 YEARS since she lost contact with crew. At same time there is mentions that its "500 year mission", that some software licenses expired due long time and so on.

if it was intended to be this long, why Rachel whines about being "ancient artifact" in case of returning on Earth?

2) Why the hell they all was so stupid, unprofessional and crazy? Lark killing Expedition Head to be in charge and then ruin everything. Its also stated in datapad, that expedition was rushed, but why? Why rush if its was intended to this long?

3) Thats wrong with Earth? In one datapad crew member writes that he will rather die then return to Earth. Numerous wars for resources also mentioned.

4) Where is, again, another expedition? This one was sent, failed, gone silent for years and nobody ever sent another mission to investigate? Why? Is there anyone alive on Earth?

5) Whats wrong with JULIA? Ok, she made submarine crash to prevent Lark from destroying jungle dwellers, fine. Buy why killing spree for everyone else? Crew wasnt happy for that they done on Ambrosia. And that "I planned to leave you in cryosleef for eternity", whoa, how mercifull.

6) Thats wrong with Rachel? WHY she was "cryo-jailed"? Why JULIA tells that she was betrayed right from the start? What about "suspicious fact" Darlington finds about cryo-jailing of Rachel? Why she was "jailed" if JULIA have no problem waking Rachel once she got some meteor damage in hull, after years in space?

This game is full of plot holes. But for fun, I'll try to answer these anyway.

1) I think what Rachel was really whining about, was being alone. Being an "ancient artifact" wouldn't have been such a problem for her if the entire crew had returned to Earth alive, because then the other crew members would be as ancient as she is. Then she wouldn't be alone.

2) Probably a combination of reasons: politics, fear, distrust (and later on, Julia's manipulation). The game's plot really goes to great lengths to try to show the worst side of humanity, but kind of handwaves the triggers for that. Anyway, I interpret Lark as a soldier (mercenary?) whose ability to think straight has been somewhat damaged by all the battles he's fought. But the real reason he took command, was probably just that someone who was sponsoring the expedition had instructed him to. The "rushing" was probably just because this person also did not want to give anyone time to kick Lark out of the expedition. (Still, why they would go to so much trouble for a 500-year expedition is unclear.)

3) Wars may be a good theory. Rachel also makes some comments that may suggest a climate crisis.

4) It was said that this spaceship cost as much as 3 wars. Earth wouldn't be able to afford another. Also, it's possible Earth didn't really expect to hear from them for a while; they might not have faster-than-light radio. As for whether Earth is still alive, the game seems to deliberately not answer that.

5) True, the crew wasn't happy, but they did let Lark get away with genocide. They did not try to stop him. From Julia's perspective, that made them all complicit, and all deserving of death. Julia's an AI who doesn't think the way a human would, probably she wasn't programmed for this kind of situation.

6) This is answered in the DLC ("J.U.L.I.A. Untold").