A question about the advances in technology; possible plot hole (spoilers).
So, the aliens were worried that our technology advances faster than theirs because of the fact that they kept having to start from scratch, however, now that they have left their planet, this would no longer apply, since there’d be no more natural disasters.
This means that in the 400 years it takes to reach us, their technology could now advance at the same pace as ours and since they’re so far ahead of us, it’s unlikely that we’d ever catch up with them.