Previously, there was an implicit understanding that the Great Firewall was in place to prevent unauthorised access to the Internet by the masses. This is to prevent them from being influenced by foreign media, prevent too much information leakage of citizen info (e.g. via facebook), and to give Chinese tech companies a monopoly in China.

If, however, you had the will and ability to use VPN software, the government usually turned a blind eye. Afterall, it was only a minority of people and they usually had a genuine need. In fact, this is what made staying in China tolerable. If this block does truly come into effect, they are essentially closing the door to the outside world.

China was a country of reasonable compromises before, but with Xi Jinping's nationalism, they are starting to think "why should we compromise at all?"