What we should be reaching for is a *slow* rate of change, one that human societies and natural ecosystems can adapt to smoothly. It doesn't matter if the climate ends up where it was five million years ago ... if that change takes a million years. But if it takes a *thousand* years, that's 1000x the rate of change. That thousand-fold difference makes a huge economic and environmental difference.
When I was a kid we had native brook trout in the streams near my house, but they were threatened by pollution. Then came the Clean Water Act of 1972, and now the rivers are clean enough for brookies, but the change came too late, the population was wiped out. You can't restock them because over the course of the last fifty years climate changed, and summer temperatures routinely reach levels these fish can't survive. If the *same* change from the last fifty years had occurred over fifty *thousand* years -- a rate that falls within the ranges of rates we see in the natural paleoclimate change record -- that's a very different situation. The trout wouldn't be extinct here in *my* lifetime, and in the year 52021 the range of the species would be about the same size, just a little north-shifted. Here at the southern end of that range we might even see heat tolerant subspecies emerge.
The brook trout is just a charismatic but economically unimportant species, but the same *kinds* of stresses are happening to ecosystems wholesale, and affect jobs that are tied to those ecosystems. Habitats are being overtaken by species that are disruption-tolerant -- poison ivy and oak, bark beetle, and fungi like coffee leaf rust. Now if the disease-free range of coffee were to shrink over a thousand years, nobody would notice; the price of coffee would gradually rise until it became something people drank in historical novels. But if that happens in *a hundred years*, coffee farmers lose their livelihood, economies are destabilized, and consumers experience loss.