There is more to the H-6K than modern electronics. It uses a turbofan engine which is like two decades more modern than the original turbojets. The engine has much lower fuel consumption and more dry thrust which means the aircraft has more range and can carry more payload. The airframe itself is made with more modern composite materials and hence lighter. The long distance strike and nuclear variants of the modern H-6 have in-flight refueling.
So the modern H-6 can hit targets in the second island chain and likely beyond. I would not be surprised if the sensors were able to target surface ships with cruise missiles at long distances. Absent something like the Tu-22M3 it is the next best thing and is quite likely a relatively cheap aircraft to build considering its capabilities. It basically uses the same engine as the Y-20, the D-30, and supposedly the Chinese have recently cloned this engine as the WS-18.
