Fair enough if you can work out the MDR groundspeed with sufficient accuracy... I haven't seen any ex-EFT pilot bother to do that - or to work out estimates at fix points with acceptable accuracy after having MDR'd the groundspeed.
But in a recreational flying environment, why make things so hard for yourself so that, in flight, you have to correct for not just airborne errors, but also basic planning errors? A few minutes with a navigation computer makes things much, much easier!
Where MDR certainly does come into its own is for unplanned in-flight diversions.