I agree with your larger point but pointing to GTD as evidence that the "core mechanics" work is questionable. Many of its biggest advocates have abandoned it.
> Just as G.T.D. was achieving widespread popularity, however, Mann’s zeal for his own practice began to fade. [...] Productivity pr0n, he suggested, was becoming a bewildering, complexifying end in itself—list-making as a “cargo cult,” system-tweaking as an addiction. “On more than a few days, I wondered what, precisely, I was trying to accomplish,” he wrote. [...] It seemed to him that it was possible to implement many G.T.D.-inflected life hacks without feeling “more competent, stable, and alive.”
It doesn't sound like Mann is disagreeing with the core mechanics of GTD in those posts, it sounds like he is saying that there are diminishing returns with applying 'personal productivity' methodologies, and you can get obsessed with tweaking your personal workflow to an extent where you no longer get payback.
This is a trap I have fallen into before - where you are effectively procrastinating by trying to optimise and system-tweaking your personal GTD system rather than just actually-getting-stuff-done.
Having said all that, GTD helps me personally massively. It's not for everyone, but for lots of people in senior jobs that gets so much 'stuff' in that they struggle to keep up, it's really important to have a systematic way to process it all and not drop anything. I find people who don't have a system like GTD or similar will tend to work from their inbox and end up dropping stuff.
That article is interesting, but really just talks about one guy's journey with GTD (Mann), and another guy's great-but-different proposal for higher-than-individual level changes.
I don't use GTD in any explicit fashion, but to throw my n=1 in the ring, the overall concept of personal productivity changed my life. Anything can be taken to a harmful extreme, and I was (at least) annoying for the first few years. But I grew out of it and kept the good parts, and I have no doubt that, for me, this sort of thing was hugely beneficial.
> Just as G.T.D. was achieving widespread popularity, however, Mann’s zeal for his own practice began to fade. [...] Productivity pr0n, he suggested, was becoming a bewildering, complexifying end in itself—list-making as a “cargo cult,” system-tweaking as an addiction. “On more than a few days, I wondered what, precisely, I was trying to accomplish,” he wrote. [...] It seemed to him that it was possible to implement many G.T.D.-inflected life hacks without feeling “more competent, stable, and alive.”
[1] https://www.newyorker.com/tech/annals-of-technology/the-rise... (or https://beta.trimread.com/articles/59839)