You raise a good point, but thats why space exploration is needed. Instant incineration into the sun would be nice. The sun is so hot the electrons would be instantly stripped from the molecules, the nucleus would explode releasing a storm of protons and neutrons, all things we wouldn't even notice. Instantly de-radioactivating (is that a word? lol) our radioactive waste.
Obviously this is far fetched now as it cost about a million dollars per pound of cargo carried into space. But the idea of a space carbon nano-fiber tube has been proposed before. Withable to withstand extreme heat, and tear, if launched in orbit between the moon and the sun, we would simply only need to get waste to the end of the tube oribiting between the moon and sun, rather then sending and wasting a perfectly good solar sail into the sun. The immense gravity of the sun would pull the waste through the tube, and would increase proportionally as it moved a long.
The answer lies in space. The final frontier. The never ending vast wasteland of invaluable resources that not even the human race could use up.