I am extremely optimistic about using learned heuristics in discrete algorithms like A* or Focal search or the various families of ILP.
In most modern discrete optimization libraries, e.g. CPLEX it's the heuristics and tuning that explain the performance.
I'm less understanding of using a end to end learning approach to replace a well understood optimal search routine, but that might be pearl clutching.
It just seems to me the authors missed that opportunity.