If a packet gets delayed or dropped because of congestion...
... the ISP didn't do their job. I pay my ISP so that their network won't be utilized more than about 50%. That's what I'm paying my ISP for. If they cannot guarantee that, they should stop making overinflated claims about their bandwidth.
ISPs aren't soup kitchens, I pay them for a service and they are supposed to provide that service.
After all there are standards on how high the percentage of phone calls going through a phone network have to be.