Many mapping programs would probably work OK for fairly simple routes on major roads, especially if a rider is by themselves and just trying to get somewhere.
Using Google maps still brings on the ever present and annoying issue of building a route on one mapset then importing that route into a GPS with another map version from a different map supplier on it. Might work just fine but just as easily might give strange routing anomalies or use different roads than intended.
What if the Google map that the route was made on contains a road the isn’t on the GPS internal map? Or a bridge is seen and allows routing across on the Google map but the map in the GPS doesn’t have that crossing as a routable bridge? That route will go to hell in a hand basket when a GPS like the Z-550 pr 660 tries to import and calculate it in. Again, that is not a big issue for a single rider that is just trying to get somewhere, or just out riding around.
But it is an issue for someone trying to lead a 10 bike scenic ride on a very specific custom made route with planned rest spots to link with other riders or a second ride group.
The more complex the route with many crossovers, some trackbacks, or very close roads to each other, can really bring out the devil in a route made on one map set then installed in a device with another version map, or different map supplier map set.
Then, just to add more confusion and upset things even more, start with an old route made on an old Garmin NT mapset with the high probably that some via points or shaping points are not even close to the roads shown on the Google maps.