Unfortunately I think we’ve already shown that we don’t need geological timescales to significantly alter the planet.

It kind of sounds like it humans manage to survive global warming and can get things back under control again, we could actually use our new knowledge to keep future ice ages from happening. There is probably somewhat ideal point between keeping the global temperature low enough that the natural ocean currents resume (which will also minimize the extreme weather conditions), and the point where the maximum available land space is available for humans to settle (because that’s just what we do). Hopefully in the future we would also keep other species in mind when trying to find the “ideal” point.

Beaver dams are only helpful because other organisms have learned to make use of that niche. There are already bacteria which have learned how to consume plastics, and others which have been shown to break down oil spills. Nature can fix anything we throw at it, given enough time. Humans may go extinct because we can’t adapt fast enough to the changing conditions, but something else will always come along eventually that can make use of the waste we create.