It's not a new tax it's existing legislation that was not enforced. By law they (the government) have a right to review your income in foreign currency for the past 5 years. So now freelancers are being taxed for those 5 years and are expected to pay, potentially thousands of dollars, in a short time period. Most of them knew this way of working was in the gray area at best and that the law is just not being enforced.
There was always an option of opening a small business, paying relatively small amount of taxes and doing it legally. This way you get medical insurance, and at least some pension. Of course this is not a good option for people that freelance as a side gig since taxes could range between 100 and 400 euros depending on what type of freelance jobs you did and where you live.