"it would be extremely difficult to define "science productivity" as an objectively measurable quantity"

Stepping back from the original article, what I would say is that a lot of the problems in academia are perhaps caused by inappropriate rewards systems based on the idea that academic research productivity can be measured over reasonably short timescales.

I'd actually be more in favor of much less overt short term performance evaluation for academics and accepting that some will, undoubtedly, squander this privilege while others would, I believe, more than reward society for this trust. Of course, this would probably be unacceptable politically as the emphasis there is often to minimize the negatives rather than to maximize the positives.