Currently a pilot has to click on 0/0/0 to enter a plane. But most people did not find this spot, they are clicking on the cockpit and try to enter the plane there.
Move the entry point of the plane to the cockpit for the pilot. Or add a "Link" in the cockpit that activates the entry point

I thought this could already be done by changing the hit boxes in the plane config. Am I wrong?

the hitbox only defines spots where a bullet is count as a hit.
There is a option to adjust the place where the pilot is sitting, but that's all, its not the entering position