To be fair, everything earlier than 200 years ago is irrelevant. We’ve built our current society and civilization in the current climate. If it changes too fast and too much, we won’t be able to adapt in time and our society and civilization will be damaged or destroyed. That is what we should aim to prevent.
Whether it was even hotter while we were living in caves, or whether a couple million humans could survive the climate apocalypse doesn’t matter. If it comes to that point, we’ve already failed.