With most of my walking being in Kent and a lot of that in woods, I know exactly what you mean.
There are of course many reasons why maps often don't reflect reality in woodland. Paths get blocked by fallen trees and undergrowth or they get flooded or extremely muddy and people make detours which can quickly become new paths.
Just a few days ago, my wife and I were walking in Blean Woods, which at 11 sq miles are very extensive. I had my GPS and we were following a route I'd plotted using the OS map. At one point, there was no sign of the path we wanted to take so we followed another that went in a similar direction - keeping an eye on our actual position by GPS and how it related to where we needed to be. Eventually we came across an unmarked path that got us back on track.
Later, we arrived at a junction I know quite well; it's roughly in the middle of the OS map below where no fewer than 7 paths meet. We wanted the path that passes just south of the reservoir, but even with GPS we followed the wrong path for a while before retracing our steps.
People who can navigate in woods such as these using only a paper map are clearly better navigators than I am.