Are you asking what the living baseline would be if there was some kind of global socialist government, and everyone was cut an equal slice of the global income and global resource pie? It would be pretty hard to dial that in because there are so many intertwined factors. But we could be pretty confident it wouldn't land near current first world standards.

No one knows what the end game of capitalism looks like, because we landed on the system because it is largely self-regulating and has worked well for carrying society forwards for the last 400ish years. Everything else has done poorly and kind of sucked.

I disagree. We've seen the endgame of capitalism a few times, and every country decided that was not right. Hence we introduced socialist policies. Like antitrust policies, social security, and nationalized Healthcare (among other necessities).

Meanwhile, I'm not sure if we've truly seen an endgame socialist policy. Captialism seems to turn into imperialism and break that up before seeing the endgame there.