Following on from NorthernSky's comments .. one doesn't need EFIS and other fancy toys to execute a steady descent path angle - albeit that the toys make the cockpit presentation prettier.
All it takes is a quick think about overlaying the desired descent, incorporating reconfiguration a la ILS profiles, on to the letdown plate restrictions so that no requirements are busted.
The normal ILS configuration profile often needs a little modifying, but the end result still maximises the probability that the pilot will detect undesirable trends - which is the big difficulty with the dive and drive school.
Certainly, there will be occasions when the steady approach results in a miss - is that such a big problem ?