Seems a bit silly to decide that “capitalism” is the majority contributor to climate change when the country that produces the most greenhouse gases is only “pretty capitalist” doesn’t it? If capitalism is the major contributor, why don’t more capitalist country produce more greenhouse gases?

That's not necessarily the case. The pollution comes from where manufacturing is, not necessarily where consumption is. The demand is coming from capitalist countries.

Edit: To account for this, we can look at per-capita consumption-based emissions (thanks to @boonhet@lemm.ee for the data link).