It was a course on data structures, not on the C++ standard library. Referencing counting would have been the wrong thing for the lesson on doubly linked lists -- which was basically the first lesson of the course. "Modern" C++ would not have helped at all for the student who had a function with a missing return statement and a confusing error log.

Frankly, almost none of the C++11 features are actually useful for teaching data structures, and those that are relevant would only confuse students. Basically, only auto and the three kinds of smart pointers are relevant to an introductory data structures course. At the end of the day those would only create as many problems as they solve. For example, unique_ptr means that there is only one "owner," right? Wrong, get() returns a raw pointer to the object, and you can make a new unique_ptr from that. Sure it is easy to avoid -- if you are an expert with lots of C++ experience, who follows coding guidelines and all that. The data structures students had little to no C++ experience and would almost certainly have done what I just described -- and that is just one of many ways they can and will screw up C++11 features.

At the end of the day, C++ is too complicated, too poorly defined, and has all the wrong abstractions for basic CS courses.

So you were basically teaching C? How does C++ come into this discussion at all?

How do you teach a basic data structure course in Python?

Pascal seems like a much better choice for data structures than C or C++. Or you can use Scala and teach functional data structures if you're adventurous ...