That title may be a bit of an overstatement. But there is a fundamental truth here: The main challenge is not to figure out how to get through a task list of 1,000 things. The main challenge is that there are constantly hundreds of things that are trying to pull us away from what we should be doing, from what is most important.
Most of those are good things. But if you attend to all of them, you will not be able to focus your efforts on what is truly most important for you to be doing at the present time — the present day, current week, current month, current year.
Having everything captured in a well-organized system that you review regularly allows you to see, within those things, what is most important. And, therefore, which things need to be chopped off so that you can truly, effectively, get those most important things done.