Is it overdone? Yes, but so are many scenarios. The question is, do you bring something fresh and interesting to the story? Canon is the right word to use as there is a lot out there.
Watch a movie called After Humans. It is rather enlightening. The question it asks and, to some extent tries to answer, is how long would traces of human civilization last were man disappeared? Nature takes back the world quite quickly.
Many years of nuclear winter and five percent of man survived? How? With nothing to eat for so many years, such intense cold - might only be preppers who might survive and not a nuclear winter.
If you want to have a small handful of survivors, a global epidemic would work as natural immunities exist. Some few might become ill while the rest die or might not even become ill at all. A BBC series Suvivors dealt with the aftermath of a plague and the handful of survivors, mourning their lost, move on to try and rebuild.
If ambient radiation killed the plants and the animals - how did any of your super powered survivors live? How did any survive? The utter destruction of the food chain would destroy the apex predator (us) along with it. No plants, so no agriculture, no animals so no animal husbandry. Are they cannibals?
Regarding the reader’s inference of nuclear holocaust causing super powers and destroying all life but man - not quite. In the Mad Max franchise, we are shown a world after the end of civilization and what happened is left unclear - until a later film when a child recounts the history of his tribe.
One thing I have noticed regarding films is that if a particular amount of time passes - a decade, sometimes two - remakes that are nothing compared to the original are made to introduce the story to a new generation. Much the same happens with books.
My nephew watched Avatar - touted to be so original - and saw it as a retelling of the Song of Hiawatha.
A more likely scenario regarding the effect of radiation is a reduced lifespan due to increased incidence of cancer combined with the lack of medical knowledge and skill to treat it.
Japan is the only nation to be bombed with nuclear devices and those were much weaker than what are in current arsenals. Look at some of the images of the survivors.
You need a scenario that will leave nature more or less intact and destroy most of Man. Pandemic can do that. Long term drought in the wrong places can be devastating.