This issue is too political for normal people to properly understand. I don't mean to offend you personally but there's little value in the feelings of someone who's been immersed in a social atmosphere of global warming propaganda, calls to action, and pressure to shut down dissenting voices. Even scientists can't safely publish work on positive effects of climate change or areas where it's not as bad as previously thought without littering their papers with defenses of "but it's still bad".

Your GP said "we must" do some things. No, there isn't a single obvious best answer. We don't know what the longer term effects will be and whether building protection will be enough or not - or enough to pay for their useful life. We don't have accurate science for that. Even if we did, we've still got hundreds of years to prepare, and importantly, future money to spend on it, which is cheaper than spending money today because of the time value of money. Every solution costs money and it's no obvious which one is cheaper.

Where did you get the mass extinction and "entirely destroy life on the planet" ideas? I know there are frequent extinctions of insects and large mammals, but that's been going on for centuries and is nothing to do with global warming. Global warming might exacerbate that but again, I don't think we have clear predictions of whole food chain collapses.

EDIT: I see you've toned down your comment from a strong belief to a suggestion of a possibility, so the main motivation of my reply doesn't really apply now.