But the default ATC never tells us to go direct when we already have a fully established flight plan.
This is why when I use the default flight planning in the world map. I always set a departure gate, then arrival gate. Then I choose the arrival gate from the drop down menu (this will assign me the approach to the active runway) Then switch to IFR, select the SIDs that departs from the active runway, select the STARs that will line up to the active runway.
Then I would have a fully established Gate-to-Gate flight plan with assigned altitude, and assigned SIDs, STARs, and Approach. Once I start fliying there’s no need to change the flight plan. Everything is established, and the ATC will follow the flight plan to the letter. No change, no clearance request, no weird altitude assignment. Been doing this method and it’s been a bliss to fly.