Stop me if this idea has been done before:

Ok, so humans die off in a world war started by global warming causing food supplies to dwindle and tensions to rise worldwide. The details don't matter, whatever, the important thing is humans are suddenly gone or almost completely gone.

Suddenly the billions of domestic animals that we keep as pets or produce are left to their own devices. Because our overproduction of these creatures has led to huge unnatural numbers of them, this leads to them overrunning the planet and completely fucking up the environment, as they envelope most of the planet.

Billions of years pass and the planet is unrecognisable with a whole new ecosystem-based around creatures that evolved from dogs, cats, cows and chickens to fill every niche. By now it might as well be an alien planet.

Sentient beings eventually evolve and discover some human ruins from billions of years ago, before the humans died out. Two religions form out of this discovery. One that worships humans and sees them as bringers of order. One that sees humans as evil demons, slave keepers and enemies of their ancestors. Needless to say, this causes conflict between the two religious factions.

The pro human faction is super fashy and expansionist, basically making the same mistakes humanity did. The also are trying to bring back humans through fucked up religious rituals.