To add on to this, I dont think you have to choose between persuing progress within the current system and building support for revolution, rather persuing progress within the current system shows the proletariat that your movement gets shit done and the two objectives work in harmony. The biggest concern is making sure reformists or other liberal movements do not take credit for any gains made and use them as proof that complete liberation is possible under capitalism when in fact it is not. The revolutionaries have to be seen as the champions of this progress in the eyes of the masses in order to build support for revolution.