i have finished a 3500 word report covering part of this topic, lack of situational awareness is the biggest cause of CFIT, it rarely has anything to do with the glass cockpit, but a lack of skill in interpreting the data given to the pilot, and with the addition of synthetic displays and top down moving map displays, the chances of CFIT are greatly reduced, certified or otherwise, its getting harder to not know where you are in relation to terrain. not to mention most if not all GPS units now come with terrain warning, even small handheld units.
the other biggest contributor is bad weather, though the resulting accident is not what would classified as a CFIT, more uncontrolled flight. usually a spiral dive manoeuvre.
Most large aircraft CFIT accidents have been the result of the crews failure to understand their position given the data at hand,(most before the widespread use of moving maps), a mis interpretation of that data, or the aircraft automation being in the incorrect config, or mode.