If humanity does end up accidentally terraforming the planet to get to hot in a positive feedback loop, I believe we will be within a line-of-sight to terraforming it back in the other direction.
Technology has solved all our physical problems so far. Maybe we will seed clouds in the upper atmosphere to reflect a lot of energy back into space. Maybe we will find something useful to do with captured carbon (which doesn’t just release it). It is insane to suggest capitalism won’t solve this problem by the time it actually needs solving, and therefore needs to be shut down (it’s the thing that actually works).