The terms Left and Right were supposedly coined during the French Revolution to describe the seating arrangements in the parliament. Those seated to the left tended to support more radical changes of the revolution. Henceforth, the Left usually refers to the more radical, anti-establishment side, as opposed to the more conservative, pro-establishment side.
For example, in 19th century France, the Left supported the republic, while the Right supported the monarchy.
The Left has since been associated with liberalism, socialism, and communism.
So what happens when the traditional Leftist becomes the establishment? In Hong Kong, the political parties and unions friendly to the Chinese government were called Leftist in the days of the colonial government prior to 1997. And rightly so, because they were opposed to the then establishment in Hong Kong - the British colonial government.
What happens now? These same parties and unions are standing on the same line as the government. They are now the establishment. They are now doing their best to preserve the status quo, to hold on to the power that they have acquired. They are making the best use of the laws, the courts, and the police to preserve their power. They are opposed to more open elections. They want to preserve the special power through the so called functional constituencies. It is clear which side they are on.
They certainly do not represent the progressive forces in society. Shall they still be called the Leftist? Probably not.