I would try to avoid the major highways as much as possible, and I have been travelling the same route for the past 3 weeks. However, every time when Waze plots my route, it would always lead me tirelessly to the major highways, which is always plagued with heavy traffic jams and accidents.
I even checked the "avoid major highways" checkbox, and yet, it still decides to lead me into major highways!
So, this begs the question, does Waze really learn your most frequent routes?
IMHO from my experience the learning of routes seems to be done on the client, and gets reset every time there is a mapdate. I assume this because when the mapdates were monthly, the client was learning my routes, and then as soon as the mapdate happened, the generic routes would pop up again.
On the other hand one of these days there was a glitch where the client was showing the preferred route heart, so I'm sure Waze is sorting that feature out. Give them some time.
Now about the highways, I've also learned from experience that any route with more than 10KM will prefer freeways and highways, so you should ensure, as an editor or ask your local AM or CM, that any viable alternative route is properly marked with the right segment types. Basically, in my country, if it's a road that connects localities (which in practice has a proper "national" number), it's a highway. In other words, don't assume a highway is a two+ lane big road or something, but instead it's whatever should be used to connect one locality into another.