It's more like your argument forgot to account for fossil fuel demand elasticity and the reason why the developing world emits less CO2 per capita. It's not because they are enlightened minimalists who care more. It's because they are being outbid by the developed world.

For every amount the developed world cuts fossil fuel usage, it makes it cheaper for everyone else to buy. Price goes down, demand goes up. Usage doesn't go down, it shifts. This is a self defeating strategy. Your theory of global emissions reduction only works if no one changes their behavior in response to supply/demand changes.