Just what IF dogs were not considered a "property". Some groups would love that. And it's not unthinkable. And it would only mean a change on the legal issue, not the moral one.
If dogs were not property, what would they be? Independent beings responsible for their own actions? Legally and financially responsible for their own care and well-being? No, they'd just end up strays that still occasionally get hit by a vehicle.
Of course, there is a fringe group that thinks pet ownership is our generation's slavery, that pet ownership is cruel and unusual punishment. Never mind that my pets have leisurely days with plenty of food, sleep, fun, and exercise, while I'm the one that legally has to deal with their excrement on the sidewalk. Who's the slave in this arrangement?