There's no such thing "no system" unless you're just shooting the CB in any random direction.
If you look at the OB, the CB and the pocket, your brain is using a very sophisticated system (you might call it "Feel") to determine the correct shot line. Your brain is making hundreds of Yes/No decisions...a "system" just gives you a couple of guideposts along the way to keep your brain/thoughts on track to the final goal. It could be that you've done it for so long that you don't think much about it (like driving a car), but your brain is thinking about it.
I use a system on every shot. Sometimes it's an Equal Overlap system,sometimes it's Allison Fisher's advice of "aim for the spot on the ball furthest away from the pocket, and sometimes it's just "this looks right to me." But they are all systems.