Durham Region to York Region... any safe and easy way?

I'm planning a bike visit to see my folks... Oshawa to Vaughan.

I'd really rather not take the waterfront trail and then twist around through residential roads, as it would easily add 20km and quite a bit more time to the ride.

But... Taunton/Steeles, HWY 7, and other options either seem to have half-measures for cyclists or sections of nothing (not even a shoulder).

All the heatmaps (Strava, Ridewithgps, Garmin) seem to suggest that people cycle on all the east to west roads, but I find that really hard to believe.

Any ideas or suggestions?