It never ceases to surprise me that people routinely emerge from what is, by common consent, one of the tougher IR training processes, lacking the ability to file basic airways flightplans and to determine routings. Similarly, the lack of familiarity with basic IFR procedures when operating to and from non-IFR fields is widespread.
There are three groups of pilots:
1) Those with ops departments
2) Those without ops departments who fly routes
3) Those without ops departments who fly locally or only on routes that are so well established that they don't need to know how to make new ones
I think group 2 is small. The training issue might well be that the IR instructors move from group 1 directly to group 3. They have little practical experience with real-life routing.