Yes, I agree. What works for me however is a fairly complex system (although the complexity is hidden in everyday usage) that took me several hundred hours to build, write and refine.
Taking notes is not so hard. Feel free to use any paper in your reach or any software capable of storing text. The hard part is actually using these notes. Getting something out of them. Relating them to other notes. Actually thinking "hey I have note for this?!" months later and executing on that thought. And then still have an input mode so casual that you also still input notes into your system.
Of course you can elect to care or not to care about that, same as you can elect to not care about properly sharpened knifes, identifying birds by sounds or child rearing practices.
But as with most things, if you care to do it well, it's anything but trivial.