I know there have been very good stories that are, at their heart, parables about things like protecting the environment and so on. But, maybe it's just that they are done lightly, instead of heavy-handedly. I don't know many readers that enjoy reading books that seem to be preaching or sermonizing on a social topic.
There are otherwise completely good and honest people on both sides of such issues as god, religion, human made global warming, politics etc. who don't want to hear that they're on the wrong headed destroyer of worlds side of the argument and thus need a college level lecture in the middle of their entertainment escapism novel. Not so many on the flat earth, gravity doesn't exist if you believe strongly enough/have pixie dust, aging can be reversed by yoga, the moon is made out of green cheese and other genuine adult believers in such things as santa clause and his reindeer.
Yet I think it is when exactly you try to treat people in the first group like they are members of the second while happily ignore the second that the real trouble begins.
For the most part people come to us for entertainment. saving a world from ecological collapse, racing against time and begging borrowing or stealing ancient elder tech terra-formers can be fun, being told that humanity did it and our current path of living in real life leads to total annihilation isn't. Having angels, magic and demons return to the earth is or can be really cool but writing that atheists are suddenly being dragged down to hell as a natural result of angelic activity is going to offend a lot of people. And honestly where's the fun in it?
The Deposed King