They don't need to. Chinas CO2 per capita is over double the sustainable level. That's how high the bar here is, anywhere even half developed is massively too polluting.
You need about 2/3 of the globe not just to stop GROWING emissions but to actively cut them.
The developing world's growth is largely fueled by consumption in the west - and the current CO2 in the atmosphere from the last 2 centuries was largely from the west as well.
The financial incentives to pollute are too great for developing countries. We can't expect them to bear the full brunt while Americans are buying F-150s and denying its existence.
You need about 2/3 of the globe not just to stop GROWING emissions but to actively cut them.