In part, this is because they are now competing in a pool made up of many talented and committed people in which it can be more difficult to stand out. But some university assessments also give less feedback and less guidance than they should. That's a problem and one that universities are addressing. The frustration for lecturers and tutors, on the other hand, is that sometimes students don't bother to pick up essays and assignments or that they just look at the grade and ignore assessors' comments about successes and shortcomings and our directions for improvement. There's not much point submitting an assessment task if all you're interested in is the grade.
Assessment works only if both of the people involved play their part.
The good assessor explains and justifies the grade, showing how future work can be improved, and the good student prepares work that responds to a task, accepts the challenge of the question or problem and finds out what worked and what didn't. Mark Peel lectures in history at Monash University and helped found the Monash Transition Program.