A cynic would say that the main activity of SI's Research Fellows is to type up their Science Fiction and Philosophy musings and upload them as PDFs to their website. Someone less cynical would say that these musings are fundamental research in the area of self-replicating AIs that will enable other people to build said AIs in the future.
But the appropriate area for fundamental research is in explaining consciousness and intelligence so that in the future someone trying to build an AI can actually define what they are trying to build.
That kind of science takes large scale organization and specialization by each person in a narrow field. It carries enormous organizational costs. It's also frequently quite a lot of boring work.
Easier to just speculate on a wide area of interesting topics while you wait for people to do the real work.
Looks like I leaned so far towards the cynical interpretation that I fell over on it.
I tend to lean toward the cynical interpretation.