Are you familiar with Rutger Bregman and his book Humankind? That gives a fresh perspective into humanity. One that I believe to be true. We're just too deep into the illusion of evilness, that's mandatory for status quo.
How about an Android OS stripped from everything that's not needed?
To be used with older devices. Privacy focused with an intentional black and white display. Plenty of devices laying around. The stripped features should also improve the battery life as well.
For IM I really loved BitlBee, maybe the mandatory IM could be within terminal. Notifications could be highly customized and the ux would be non-candy one.
To some parts this is a matter of education. It's been studied that few years of economic school makes people more greedy and selfish so I'm tempted to think that it'd also work the other way. And what is the capitalist society for people living in it if not a school of economics.
Setting a cap and communicating the target for personal emissions would be unkind to all billionaires and politicians. Thus aint gonna happen. Also this way of thinking will hilight a culprit. One that definitely doesn't want to be hilighted.
Besides the normal peoples guilt will be a huge blocker for anyone to even start thinking about personal cap.