I think you're looking for points to argue on and prove your superior understanding of economics and fair labor, and in the process brushing away important points and ignoring the insights of peoples' comments.
You've asked for more context, so here's what I have that is not talked about in the article.
Leading up to 2006-2007 and the financial crisis, these entry level jobs were salaried positions with standard benefits. Obviously this sounds expensive for a company, and there's plenty of arguing around whether this is worthwhile, but arguing won't help build the context.
During the financial crisis, as companies scrambled to cut costs as much as possible, a trend began to emerge. Companies realized that rather than give salaries and benefits for these entry level jobs, they could hire new grads and anyone else unable to find a job to be unpaid interns, doing the some level of work -- sometimes more depending on the person and position. I hope you would agree that not paying people for work is taking advantage of them. This is obviously more extreme than the contract practice talked about in the article. After it became clear companies were taken advantage of the job market to get free work out of desperate people, states began making legislation to make unpaid internships illegal. Here in California, it is illegal to not pay an intern if their work contributes to the business in any way.
Now that businesses can no longer get free work, they have reacted by filling these positions with hourly contractors who get no benefits whatsoever, no PTO, no sick days, nothing. Salaries for these contractors are often very low. 25-35k a year based on the hourly work. Salaries aren't being dictated by the value of the work the employee provides the company, but by the difficulty in getting (and really going through the process of finding a new job, possibly relocating, etc.) employment elsewhere.
The contrast between these positions 6-7 years ago and these positions now is why people say (feel) they are exploitative.