The value of enthusiasm should not be underestimated. Many times older, more experienced devs will have learned-helplessness issues around a technology or merely think certain things cannot be done. Or overengineer things, thinking a O(n^2) sorting routine cannot be seriously considered, but a good routine makes the problem so complicated the problem is impossible to carry out. Whereas a junior dev will not know what the fuck many of those things are, use the bad sorting routine, and actually solve the problem.