No planner can possibly be perfect for everyone. You need to meet the planner half way sometimes and change what you do to get the most out of it. Even if it's totally perfect for your needs you still have to do stuff like carry it around, consult it, write in it until it becomes what the GTD crowd call your 'trusted system'.
Whenever you make a change - and adopting a new planner or planning system is a change - you need to persist until it becomes a habit, until you can't even think about not doing it. This will take some time.
Some people have trouble because they're not terribly organised. Just having a planner won't fix that. Some people have trouble because they are organised and disciplined enough not to need a planner, so the planning is just additional overhead for little gain.
Work out if and why you need a planner. If you do, and you know why, work to find a routine that gives you the planning support you need. Force yourself to use it until you don't need to force yourself any more.