I have a friend who has a Hyundai Santa Fe - two years old - that she has told me has live traffic updates in it's inbuilt satnav.
I think she said it is a subscription based system, though...but it is free for her for now.
I agree though that, in general, most satnav units aren't that sophiticated so aren't going to help with live traffic updates.
My three year old Mazda3 supposedly has live traffic on the native satnav but it's useless because the internet connectivity via my phone doesn't work. It's one of a few things that has made me gradually get increasingly annoyed with the vehicle over the time that I have owned it.
I don't intend to pay $600 to have CarPlay retrofitted to this vehicle, but I will make sure that my next vehicle has it because on rare occasions when I need maps I would much rather have them from my phone than the vehicle's satnav. At this stage the Hyundai Ioniq hybrid is looking like my preferred option for an eventual replacement.
I have driven an Ioniq and LOVED it...if the range suits you, it would be a great replacement for your Mazda 3 :-)