I generally disagree with the premise that scientists are becoming less productive. (To me, the complaints that there are no more grand fundamental discoveries is alike to complaining that we are not discovering any new continents on Earth...)
On the subject of incentives in academia - reflecting on my academia run, I've noticed that I was the most creatively productive when I had a longer planning horizon in front of me. It was either at the beginning of a several-years position. Or at the very end when I knew that I'm leaving and didn't care anymore. The least productive was the sequence of one-year postdocs - when I was constantly worrying about the next one.
On the subject of incentives in academia - reflecting on my academia run, I've noticed that I was the most creatively productive when I had a longer planning horizon in front of me. It was either at the beginning of a several-years position. Or at the very end when I knew that I'm leaving and didn't care anymore. The least productive was the sequence of one-year postdocs - when I was constantly worrying about the next one.