The author of this article wrote Deep Work, which stresses the importance of, well, deep work over more shallow tasks like responding to emails (it is stressed that shallow is not intended to be a deragatory term).

I've seen his opposition to GTD expressed before and was excited to see it in long form, but left a bit disappointed when it was essentially just recommending a kanban style approache and some limitations on interuprting another person. I understand it is an open question though.

Though I do empathize with the addictiveness of productivity systems. As mentioned, it disguises itself as a form of productivity and can be easy to get carried away.

I think ultimately it comes down to how one implements their GTD system; I use it to offload stuff I don't want to worry about remembering (including outlines for projects), and am careful to limit my view to only what's currently on my plate. This allows me more time for 'deep work', but this work however is extremely unstructured, and I've come to learn that's a feature and breaking it down into a GTD style checklist is not at all effective for me. I think that's why it may be hard to come up with an equivalent system for deep work; it just doesn't lend itself as well to a GTD style approach, so perhaps my criticisms above were misguided.