I think some influential climate scientists transition away from science into politics (Mann, Hayhoe, Dessler). They offer up commentary that will sway public opinion and make headlines. That is how politics works. I don’t think it necessarily means climate change isn’t real but you do have to be aware of how the political apparatus operates.
Agree that comments like “the world is ending in 12 years” will ultimately become an albatross for the climate folks, but at the time it galvanized a lot of support. The issue with climate is that it’s a long term issue that will never affect anyone alive today meaningfully. At least not so much as to change your lifestyle because fossil fuels provide so much value. The trade off is incredibly one sided. That could change in the future (like 300 - 500 years or more), it also might not. The question is, do you want to roll that dice?