Waze claims to do something like and it produces the most retardedly slow routes ever. I just hate it when someone uses Waze on my Lyft because I just know I'll take 10 minutes more.

I don't think it's as trivial because there are lots of things to consider. Some drivers are just SLOW and it will have nothing to do with traffic. Maybe all slow/terrible drivers use your app so all the route speed information is completely based on specific patterns set by your app.