Knowledge workers put too much attention on "productivity" and "productivity systems".I know this because I'm guilty of it.
Every day one has an endless amount of work but only limited mental and physical capacity. So we look for short-cuts, hacks, tricks—whatever you want to call them—in an effort to do more in the same timespan.
Anything from the Eisenhower Matrix to David Allen's Getting Things Done to the more recent PARA method by Tiago Forte are all attempts to help us manage our physical, mental, and digital inboxes and do more stuff.
In my experience testing some of these systems—and multiple to-do apps—I found that work is treated as a long list of tasks that one needs to go through and mark as done.
But most work is not linear. For example, when working in a fast-paced environment like startups, projects and priorities shift so fast that it becomes a challenge to keep the productivity systems in place.
Moreover if one manages to keep the system up and running, there's always the problem of being effective vs efficient. Since these systems are tailored for shallow tasks one risks being efficient in doing work that's not really needed.
In my experience, a better approach has been to schedule time every day to focus on just one task and start working on it after I've proven its utility in the broader context of the project I'm currently on.
Productivity doesn't require complexity.