In my experience one of the big problems is that negative results are not published. So it is probably more common than generally recognised that obvious hypoth

In my experience one of the big problems is that negative results are not published. So it is probably more common than generally recognised that obvious hypotheses have been explored in the past and found to be false. The key premise of PhD research is to expand the body of knowledge. Incremental results under an experienced PI are easier to come by than substantial steps outside of the popular research areas.