Certainly one day the system will be unsustainable. You can sustain growth for a little while with a stable population by increasing consumption, but once the succeeding generations have the same number of buyers or fewer, it becomes very challenging to find new dollars to buy more goods.

As to your question about the snap... 3.5 billion would be an economic disaster and because people have fewer children it would take forever to rebuild that wealth.

> There's an issue with that thought, won't it be unsustainable after the population reaches a certain threshold?

Perhaps, but the hard limits set by physics are probably ludicrously high, and the soft limit set by physical and social technology can, in theory, improve alongaide population until they hit the hard limits.

I'm worried about the shocks, not about the decline itself.

I mean wouldn't it be better if the changes were more gradual?

> I'm worried about the shocks, not about the decline itself.

Yeah, in the long term, we’re all dead. The path is all that matters, not the steady end state.