Empires rise, empires fall. There are brief pauses between endless wars and nobody ever gave a rat's ass about the good of humanity.
But the good happened incrementally, because the mechanism of economic growth required reality of some sort, something to be produced, to be sold, and people to make it. Now, that is not the case. Wealth can be made with no attachment to the physical world.
If anything I see the world after World War Two as almost a golden age of humanity,
Up until the early 70s. Then shareholder wealth became the driving force, as did using debt to extract from the masses.
What comes next is unknown, could be a WW3, or AI Apocalypse or Terminator type future, or could be the biggest golden age of humanity so far has known...
The last is the least likely.