It's not capitalism because authoritarian states aren't cutting emissions either. Capitalism gives the people with money what they want, autocracies give the people with power what they want, and so on, and not one single distribution of getting-what-they-want is going vegan and cutting emissions to zero. The only remaining conclusion is that nobody wants to go vegan and stop emissions.

If you want a government that does that, you would have to give all power to a small group of people like you. That would never happen because there are so many groups with other immense interests that if you are going to let one "win" and control everything the odds of you winning are almost nil. The only option is to somehow get more people to want to change everything.