Varies greatly by area. I live in a big city in a still sketchy, slowly gentrifying area with fairly high serious crime rates, and do a fair bit of research and consulting work with the local police departments. The ones in the city do pretty much no dedicated traffic enforcement. They're hundreds of officers short of their legally mandated staffing levels and struggle to keep up responding to crime calls, traffic accidents and investigations to waste time sitting with radar guns. Any traffic enforcement they do is when someone is doing something dangerous in front of them (running red lights, nearly hitting people, driving like they're intoxicated, super aggressive driving etc.)--or profiling hoping to find guns and drugs (which is wrong, but definitely still a thing despite the patrol force being 70 some percent black here in the main agency). And they do spend a lot of time patrolling the black neighborhoods, but that's because those are the poor, higher crime neighborhoods here due to decades of segregation and disadvantage and where the majority of citizen reports of serious crimes are coming from.
Now go out to the suburban departments where there aren't so many shootings, robberies, burglaries etc. and yeah, the cops are doing a lot more traffic enforcement and other petty shit. Now you are right that even the big city patrol officers aren't fighting serious crime very shift--just much more often than their suburban counterparts. Patrol officers are overwhelmed by calls here, but most are still things like domestic disturbances, noise complaints, thefts from businesses, vandalism etc. But doing that stuff and dealing with the fairly high felony property crime and violent crimes here mean they aren't doing dedicated traffic enforcement hardly at all (mostly leave that to the state police on the interstates and county police elsewhere) and the detective units are too busy with all the burglaries, car break ins etc. to spend much time on package theft. Best bet is to put up some very visible cameras--stuff still gets stolen, but that drops your odds the most of anything you can do besides just not having stuff sent to your house if you can't be there for it.
The patrolling of malls and other private property is officers working extra jobs off duty. That's private property and they aren't going to be patrolling that on tax payer dollars. That's on the businesses to pay for, otherwise they're only coming to respond to calls for service.
