(There might be one exception to that: reducing warfare. War is a gigantic waste twice over: tons of energy to fight, tons of energy to rebuild all the stuff we break. But I doubt eliminating warfare would be enough alone to cut emissions enough to matter.)
There's only two ways to reduce CO2 emissions by a large amount in a durable lasting way:
1. Replace CO2 emitting sources of power with those that don't emit CO2.
2. Destroy the middle class.
Actually I guess there's a third: kill a lot of people.
Anything less is a rounding error that won't make much of a difference.
I'll take option 1. Luckily the laws of physics say we can do it. We just need the political will. There's also precedent. Many developed countries' emissions per capita has been falling while growth has actually continued (in most cases) and standard of living hasn't moved much. We just need to do a lot more of what works.