Coming from that era, I strongly disagree. While I agree with the article, that some elements are harder to spot as interactable, I would still say that they are way more coherent than programs from W2K era and that one just got used to the broken design of the UIs of that era/platform.
While usually understanding the UI even in W2K, I don't think that the dumbing down of UI (and reducing palette/layers adds to that) for the dumb users is necessarily a bad thing. At the end of the day I am also a dumb user.
Actually using GTK3 for a while now and moving to GTK4 however might also trick me to not notice a downgrade in discoverability, so in that particular instance I might get tricked by getting used to a certain design language even if they simplify it to the point of actually decreasing UX for users that are unfamiliar with GTK compared to GTK3.