Sea no Land.
The use of Radio Aids are an addition to basic Nav. The basics of navigation to PPL standard assumes that the aircraft is not fitted with such aids as VOR, DME, ADF or the likes of GPS or that the transmitters are not available. Such well developed root of the art techniques correctly applied work well. The techniques apply whether over the sea, desert or the satilite towns of the home counties and they do not need batteries or generators to function.
That is not to say MDR is wrong. The navigation section of the CPL Skill Test is a section that has the greatest rate of failure. Why - the mistakes are usually silly - well the pilot is under stress. Simple mental arithematic becomes a burden and the visual clues, like a mirage, become what the individual wants them to be, mistakes are made.
It is a fact that there is not a single unpredictable factor that will raise it's head on a flight and it is therefore within the pilot potential to pre-plan for them. Using Forcasts winds and calculation of headings prior to flight using the slide rule and common sense mental arithmetic is part of that philosophy.
Whether or not you are a supporter of MDR, don't thow out the baby with the bathwater! Supported with the basic skills of navigation MDR has a place. Indeed it is currently taught under the heading 'Unplanned Diversion'. Always has been.