Sometimes, lacking the clear-cut conclusions of STEM is an unavoidable aspect of the type of philosophy. For instance, it's very hard to do foundational epistemology with perfectly clear-cut conclusions.

At other times, the lack of clear-cut conclusions is simply the conceit of philosophers thinking that being good at thinking is enough and that they don't need also to collide vigorously and repeatedly with evidence. But this is a natural-enough error to make, so it's worth having the views stated and argued against.