I wonder if we should assume the characters from the past, from Star Boundary, who haven't been present for the longest of time anymore, are dead now. Casualties of the long war against the ink clan or just failed at cultivation and withered away. The old great emperors from Star Boundary keep appearing, plus very few others such as this old expert of dao of space, but that's pretty much it.
Although to be fair, if the author drew many of the old characters in the background, I wouldn't recognise them anymore.