I built OSRM on Ubuntu 18. I ran osrm-routed with MLD.

OSRM demo gives a superb route. Example Route: http://map.project-osrm.org/?z=10&center=35.891831%2C-98.521957&loc=36.253133%2C-98.480072&loc=35.821432%2C-98.779449&hl=en&alt=0&srv=0

Mine OSRM server provides this route: http://map.project-osrm.org/?z=12&center=35.872777%2C-98.565731&loc=36.253133%2C-98.480072&loc=35.948273%2C-98.493805&loc=35.890441%2C-98.507881&loc=35.821432%2C-98.779449&hl=en&alt=0&srv=0

That route uses roads classified as residential, instead of 65mph secondary roads.

This is using the default car profile.

Traffic data shouldn't affect this, because there is no traffic data in my server, and the optimal route regardless of traffic is the one the OSRM demo provides.