Over time I realized that what GTD was missing (or not stressing enough) was the insight that in addition to knowing your commitments and deciding what we need to do to make them move forward we need to constantly remind us that resources are limited and priorities are not distributed equally but rather very asymmetrically. Only a few activities will have a major impact on our lives. The key is to focus on a few activities and deliberately ignore the other "80%". And while we ignore the other activities we have to learn to deal with the stress of not doing the other activities.
David Allen's method encourages people to keep lists of open issues. That's a very good practice. But it lacks the advice to implement a filter: To ignore 80% of the potential issues before we let them onto our lists. And to endure the stress that is caused by ignoring most of the things that want our attention.
Tl;dr: GTD does not stress making decisions and setting priorities enough (even though it mentions it in many chapters).