Mammals, reptiles and amphibians existed back then as well, as did a variety of plants. Uninhabitable sounds like most of the Earth turns into Venus, which won't happen. The current ecosystem will undergo change as some species adapt and thrive while others go extinct, migrate or are confined to smaller areas.
What this looks like for civilization and to what extent humans can mitigate is debatable. Climate models aren't civilization models.
What this looks like for civilization and to what extent humans can mitigate is debatable. Climate models aren't civilization models.