This reminds me of a couple of old sci-fi series I read a long time ago. Michael Moorcock's The Dancers at the End of time series about the last of humanity tha

This reminds me of a couple of old sci-fi series I read a long time ago. Michael Moorcock's The Dancers at the End of time series about the last of humanity that's become apathetic, decadent and godlike as all the stars die around them and they come up with a plan to travel back in time and start civilization earlier so humanity get get on its feet quicker, but discover time is cyclical. And another series, I wish I could read again but cannot remember the author or titles, but it was about a world where civilization ended because we'd genetically engineered ourselves and animals and everything into fairy tale creatures who overran everything. The whole time it seems like it's set in the future but it ends up the main characters become Adam and Eve and it implies all our current mythology came from the society that genetically engineered themselves out of existence.