Your "problem" has no logic.
When choosing a route, the differences are reduced to only a few places, and certainly not visible at high zoom.

Here you are not looking for roads as a pedestrian, but for a vehicle.
LocusMap is primarily intended for leisure activities.

If you want to choose your own roads, not the shortest/fastest/ best ones, then you have to plan carefully and spent much more time.
Igo will not take you to the roads of poor quality unless you insist on it. Etc etc...


You actually want to use iGO to travel outside standard routes.
For the purpose you want, you will need to combine both applications.