Even many people who aren't outright climate change deniers don't understand the seriousness of the situation, possibly in part because they've been trained (largely by religion) to see things in apocalyptic terms. If it's a binary switch, if it's "The world will be destroyed or no", any perception that we're 'over the line' will lead to people tuning out.

The reality, on the other hand, is that life for humankind on planet earth will go on... at the cost of billions of lives, worldwide political instability, and literal quadrillions of dollars of economic loss.

Each reduction we make now saves tens or hundreds of thousands of lives, improves the standard of living of hundreds-of-thousands more, prevents a war, saves billions of dollars. I don't know how we get people to start thinking in terms of "How do I improve our situation going forward?" instead of "We die or we don't", but I suspect it would be helpful.