They don't pile up too much oxygen, carbon dioxide, nitrate or phosphate. Those are kept under some kind of biological control. That's how the past has been. The big issue is, will the future work that way?
It's a valuable new piece of information. Understanding why carbon dioxide varied in the last glacial maximum is the most important question facing us. If we can't explain the recent past 18,000 to 20,000 years ago, then we can't be confident of our ability to predict the future.