Besides the causes which OP lists i think job opportunities also take a part why unemployment number increases for each year that magined, the companies only open 2 position for new employee but job applicants can reach to 1000 people or more which mean every job applicant has less than 1% chances to accept and gets new job.
I think this became an the main issues in some countries that fresh graduate didn't gets more opportunities to gets the jobs and showing their skill so, that's why currently the youth is dominate unemployement and the worst thing is the number of unemployment will always be increases following the student who graduate from the university.
I think all countries are facing challenges about unemployment on fresh graduates, because of the vacant position and applicant ratio. Here in my country there are about 4 applicants competing in every ideal vacant position. Those who are not hired will be forced to take the jobs below their standard rate.
OP was right about having a degree alone won't be enough to land a good job, one will need skills in line with what the company needs, to have an edge. Many college students these days are in a lot of pressure, from maintaining good grades, finishing up deadlines, and equipping their selves the skills needed to be competitive against the growing numbers of unemployment.