It should be noted that the force with which the contents of an exploding rocket hit the ground is not infinite, and objects have been built to withstand it. In particular, the casing of the plutonium bricks used in the radiothermal generators which powered certain space probes had this property.
You could also have a parachute at top that would open in case the engine and fuel exploded, so long as the waste casing could withstand the forces. Also, launching on a remote island could be beneficial, but it'd increase the cost. Also, there could be smaller more frequent rockets than larger ones.
