Those are all valid points but I dont think thats what OPs question was about. They asked about effective ways to fight climate change. Not doing anything can never be an answer to that. Whether or not it makes sense to spend your hard earned money on other peoples behalf is a different question.
Also, no we are not doomed. Yes, climate change will have a huge impact on humankind, but earth wont randomly explode or something. Humankind will adjust to higher temperatures and more frequent natural disasters, but the extent to which this will affect everyone can still be minimized. The poor will be fucked the hardest, 'accepting our fate' and not doing anything will cost millions more lives than it could.
Also maybe theyre adults?