What I find interesting about RMS isn't that his productivity was suspect, but frankly that it just ended in the late 80's. He still writes code, surely, but there's a big wall in his history where he just decided that the code was there and what the world needed was moral evangelism. That's a fairly alien attitude to most of us, I suspect. I certainly could never have been happy with a pivot like that.
More generally the idea that the FSF was just lolling about not getting anything done until Linux landed in their lap is a weird modern fantasy. And ironically it's exactly the kind of thing they tried to treat by publicizing (or "stealing" if you swing that way) the "Linux" brand with the "lignux"/"GNU/Linux" nonsense. They wrote a ton of working code, most of which we're still using today. What they didn't write was Linux.