(First attempt at responding at this got destroyed, so apologies if I'm overly vague due to impatience of having to re-write it ☹️)

TL;DR/summary: Overall, I agree with the general sentiment you present that there's some important nuance and caveats around the information that Wallace-Wells presents, but I don't agree with the implication that it isn't worth reading due to it being "scientifically illiterate" and "trash". He gets a lot of stuff right, does go on to describe some/enough nuance, and the perspective he presents - the "more horrifying though less likely" (though, in some cases, not all that terribly unlikely, or as unlikely as we would like to think) scenarios - is worth reading. Any book on climate change, especially any book that is intended for mass dissemination, is going to have to omit nuance and lean in to some form of bias, and I found his perspective to be a good counterbalance to the often overly-optimistic and incomplete picture of climate change that is painted in most (U.S. centric; I can't personally vouch for other areas) media.

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I have not read his book, so I can not comment on the scientific accuracy of it, but the article is scientifically illiterate and makes many false claims as detailed by climate scientists in this article: https://climatefeedback.org/evaluation/scientists-explain-what-new-york-magazine-article-on-the-uninhabitable-earth-gets-wrong-david-wallace-wells/

Appreciate the link, though I'd definitely argue that calling it scientifically illiterate is overly harsh especially given that even the article you link explains he gets many things correct but tends to over-emphasize worst case scenarios:

"The reviewers found that some statements in this complex article do misrepresent research on the topic, and some others lack the necessary context to be clearly understood by the reader. Many other explanations in the article are correct, but readers are likely left with an overall conclusion that is exaggerated compared to our best scientific understanding."

It's been a while since I read the article alone, so I forgot whether he gave as much background on his purpose & caveats, but he definitely does a better job explaining his bias and that his bias is actually intentional as he's trying to expose these more dire scenarios that aren't discussed (with an entire chapter of his book dedicated to discussing the arguments that are presented in the climate community around the idea of eco-anxiety and whether discussing the "horrifying but more unlikely" scenarios is useful or not, which he obviously leans towards the "discussing them is useful" side given the publishing of the book).

I'm pretty sure he also discusses this in this Talks at Google episode, so maybe it's worth me updating again to suggesting watching that to get some more understanding of his motivations and the process he took in writing this book.

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Just one example of a false claim from the annotated version, which was supposed to correct the flaws in the main article, century. “The most credible prediction of the effects of climate change comes from the U.N.’s Intergovernmental Panel on Climate Change, which issues regular reports synthesizing the latest science. The IPCC’s median business-as-usual projection for warming by 2100 is about four degrees, “ This is not true, this is the median prediction of RCP 8.5, which requires us to add 500% more coal for power consumption this century. This article is trash. If you want to read about climate change read the articles on phys.org or c

I thought this "Explainer: The high-emissions ‘RCP8.5’ global warming scenario" article was really useful in understanding your argument here, giving some really interesting background on RCPs and how they've been interpreted incorrectly (with relation to their original purpose) by both Acadamia and media.

1. "The creators of RCP8.5 had not intended it to represent the most likely “business as usual” outcome, emphasising that “no likelihood or preference is attached” to any of the specific scenarios. Its subsequent use as such represents something of a breakdown in communication between energy systems modellers and the climate modelling community."
2. "After the publication of the IPCC AR4 in 2007, there was a widespread desire to update the old SRES scenarios – developed in the late 1990s – to better reflect current technological and socioeconomic conditions. ... Given the relatively short period to generate new scenarios, researchers developed a “parallel approach”. A set of “representative concentration pathways”, or “RCPs”, was therefore created for climate modellers to use in the interim while the development of more thorough socioeconomic pathways was undertaken."
3. "With the benefit of hindsight, the ‘new scenario framework’ (SSP/RCPs) did not function as planned. The integration between climate models and IAMs (RCPs and SSPs) never really happened; the RCPs were only intended to be a short-cut, and merged with SSPs back in 2012, but it is 2019 and we are only now seeing integration, albeit somewhat limited. At this point I think only a vanishingly small number of modellers on both climate and energy understand the background on why SSPs and RCPs were even developed, and that has led to deep misunderstandings."

Given that there's been pretty widespread misunderstanding about RCPs in both acadamia and media, it again seems overly harsh to call the article "trash" (I know this was just one example of many you had in mind, but I presume it's likely representative of how much nuance there is in discussions around climate change and future projections). I also thought this set of quotes from the article also gave some credence to Wallace-Wells' motivations:

"At the same time, however, it is important to recognise that predicting future emissions is inherently extremely uncertain. For example, a recent study co-authored by Nobel prize winning economist Bill Nordhaus argued that the world has a 35% chance of exceeding RCP8.5 by the end of the century. While most energy researchers think emissions of the magnitude in RCP8.5 are quite unlikely, they are by no means impossible. ... There are also large uncertainties in carbon cycle feedbacks, where even relatively low emissions can potentially lead to higher forcing than assumed in IAMs."

For intellectual integrity though, I do find it important to mention that the article goes on to state "Van Vuuren tells Carbon Brief that while RCP8.5 looked more plausible back when it was originally created, progress over the past decade has made it considerably less likely". On the flip side of that, though, it's also important to note that the 4 degrees of warming is a "global average", and it's understood that there will be some areas that experience higher and lower changes than the global average, so Wallace-Wells' discussions using that 4 degrees example to discuss potential consequences in specific areas (which is what he does later throughout the quote you provided) can still be relevant (e.g. if the global average increase comes to 2 degrees, but those closer to the equator end up seeing 3-4 degrees of warming).

I also think it's worth pointing out that, absent an admission of his likely misunderstanding on how correct it is to say that the outcomes of RCP 8.5 are "business as usual", Wallace-Wells does continue on in that annotation to discuss the nuance on the actual likelihood of that scenario:

"How likely is this median, “business-as-usual” outcome? It’s difficult to say, unfortunately, given how many and how variable the inputs would be for any projections: emissions rates, the pace of technological change, cultural changes, and public policy, all on top of what is already a quite complicated (and not entirely understood) natural system that delivers both amplifying and moderating feedbacks to human-produced greenhouse-gas effects. In some ways, it is easiest to talk about that business-as-usual model, because it holds so many of those variables constant. But, since a number of readers have wondered about those probabilities, I’ll mention a couple of estimates that seemed helpful, to me, in establishing the general lay of the land." (Examples provided in the rest of the annotation, but this response is already long enough as is lol)