Beyond just not being a huge fan of the genre, Liam Neeson also knows that playing a superhero character would require him to go through some prolonged, intense and perhaps unpleasant physical preparation, and he simply doesn’t want to do that.
While Liam Neeson can appreciate all the bigness of superhero films and all the technological wizardry that goes into making them, they’re simply not his cup of tea so he doesn’t feel compelled to dive back into that world.