commuters and other area drivers have adapted to spending much of their time on arterials and local streets.
I lived in Sacramento between 2007 and 2014 and while that is absolutely true, it isn't exactly the most ideal situation (half hour drives along Watt between US 50 and I-80 were not uncommon at rush hour; Sunrise Boulevard from US 50 north through Fair Oaks was always highly congested as well).
To some degree the rush hour issues on Business 80 north of E Street were exacerbated by the double whammy of no other north-south freeway alternatives east of there (in an area where there are large gaps between river crossings, i.e. between Watt and Sunrise) and no widening around the Marconi Curve due to the limited right of way that was to have been bypassed by the canceled 1970s I-80 realignment.
From downtown to Watt, there are a decent number of river crossings (Interstate 5/Route 99, Route 160, Business 80, H Street, Howe Avenue) compared to east of Watt (Sunrise, Hazel, the two old town Folsom bridges, and the Folsom Lake Crossing). I don't necessarily think there's much Placer County to Elk Grove traffic so much as traffic from US 50 to Hazel and Sunrise to get to these arterial-only suburbs like Fair Oaks.
Route 244 would have allowed drivers heading out towards Folsom, Rancho Cordova, and the South Lake Tahoe area to avoid driving through downtown, I think that would have been the one true bypass route of some utility and would have helped out with the Greenback Lane traffic to some degree.
Interestingly, Sunrise Mall in Citrus Heights is located not far from where unbuilt route 102 and the unbuilt portion of Route 65 would have met up, I've always wondered if that development was originally planned around the freeway being there (in similar fashion to the effect the Beverly Hills Freeway might have had on Los Angeles's Century City area).