I don't know how we used to do App's pre GPS and survived? Until I drove heavy metal the GPS App's I used to do where done via the pitch wheel on the AP for vert guidance using basis ROD's and distances to go from each waypoint.
I suspect commercial pressure was some of the reason the guy ended up way behind the A/C.
The invention of satellite based navigation has been a godsend, it also has been another way of reliance on technology.