Also there was no reerntry per se - ships basically decelerated to zero and then lowered themseles into the atmosphere on continous burn acting a construction cranes. It was not usuall "burn in" orbital drop like in Starshi Troopers, more like placing large structure with the use of construction crane or helicopter, only with antimatter powered plasma torches.
Again I'm 99% sure that is not how reentering the atmosphere at any speed works.
why is earth dying when we have intersetllar ferry service running on a profit ? because we have a whole planet here we can charge access to and enslave anyone who wants to come also fixing earth would cut into profits reduce RDAs leveraged control of humanity
The movie hasn't told us what Earth is dying off.
So maybe it is something like a cascade failure.
I have no idea how something like that could happen. And I don't think a single sentence said by someone deserves overthinking it. Star Wars did that with the Clone Wars, which was a single sentence that grew into a spin-off franchise.
also
The more I think about this Whaling thing the more stupid it sounds.
So they can make an Avatar. Something that is the same species as the original. Yes, it is expensive. Why not just make a pool on Earth and breed the whales there? You can even figure out a way to milk the whale more than once.
You can handwave it way, that the brain juice being magic is a recent discovery.