As a former doomer, this post does a great job of building a flimsy strawman of doomer thinking and then tearing it down. It does not respond to any of the real concerns brought up on doomer subreddits such as r/collapse.
The fundamental stance of doomers as far as I have understood it is fundamentally Malthusianism - infinite growth cannot occur on a finite planet. The majority of people alive today are only able to eat because of synthetic fertilizers. Phosphates in particular are mined and are being lost to the ocean via soil erosion due to industrial farming practices. Freshwater is being depleted unsustainably all over the world. The EROI of oil is consistently declining. This post totally ignores the Hubbert curves that are fundamental to much of doomer thinking, and doomers only have to be right about one of them for there to be a massive population and living standards collapse.
This post also largely ignores that doomers acknowledge the mainstream climate models but believe they don't properly account for feedback loops such as the clatharate gun hypothesis. It is especially egregious that the IPCC numbers are cited, when so much of doomer discourse surrounds criticisms of the IPCC and its consensus-based methodology resulting in excessively cautious claims.
I have stopped being convinced we're doomed, but that's not because I think doomers are wrong, I just think we really might pull off the technological miracles required to kick the can down the road far enough not to worry about it. Better to look forward to space mining and virtually limitless energy than spend my days feeling angry we didn't do something sooner.
If you read Overshoot by William Catton (one of the most important doomer books), you know that there's nothing we really could have done. We will always grow into the size of container we have. So the best we can hope for is a galaxy sized container, and that's what I choose to do.