There have been reports Tesla is working on a new navigation app, which may be running in the Model 3's and in S/X cars in some countries.
If true, then we just need to be a patient and wait for Tesla to release the new app to all cars - and then we can start a new round of comments about how that software falls short. (Maybe this will be included in the 9.0 release - which should be coming out soon...)
Looking into my crystal ball... Tesla will eventually shift to using a cloud-based routing app - which would do the routing on a cloud server using the most up-to-date data available (real-time, or close to real-time), and still provide the on-board navigation routing as a fallback when the car is offline, at least until the cloud server is available.
A huge advantage of the cloud approach is that it will be much easier to keep the cloud servers running using accurate data (maps, traffic, road conditions, weather, ...) than trying to keep the data up-to-date in all of the cars.
Until we get a better navigation app, I will continue to use the onboard navigation - though use it only as an advisor and ignore the routing when I suspect the software has made a poor choice.