Is the credit assignment problem a well-posed one? Credit assignment is the process of assigning credit (or blame) to a particular move in a sequence of moves (temporal credit assignment) or to a particular node (structural credit assignment) among many nodes, for example, in a network.

My question is somewhat philosophical: Does it even make sense to speak of credit assignment as a problem to be solved?

Take the example of a football (soccer) team. (I read in a paper that robo-soccer teams face a version of the credit assignment problem). However, even in the case of a real-life soccer team composed of humans players, it is virtually impossible to separate the performance of an individual in scoring a goal from the contribution of the rest of the team in the most general case. If quantifying and assigning credit to players is so difficult, does it even make sense to try to assign credit to nodes in a complex system, with many pieces that are interacting in subtle ways?
If you can do it well, it is useful.  If you can accurately identify which move was to blame for bad outcomes -- or which one is to credit for good outcomes -- that is useful in helping you learn to make better moves.  I'll let you decide whether that's enough for it to make sense to speak of it as a problem to be solved. I'm not very knowledgeable about philosophy, so I don't know whether that qualifies.