Sure that might be true. Seems like just a symptom of success tho. At some point you start to run out of lives to save. For example, today more people die of obesity than starvation. So agricultural advancements just will not save as many lives as 50 years ago cuz there are not as many starving people that need saving.

If a society with horrible living conditions like most of the world in the 1900s gets tech, the period where most lives are saved will eventually pass as that tech succeeds in improving living conditions. If we were constantly saving millions or billions of lives with new tech, we have a problem. Where are all these extra people in peril coming from?