The left is primarily not concerned with the wealth disparity caused by different wages between jobs. What drives inequality, which makes our society less democratic and just, is the private ownership of capital (meaning means of production in this context). It would be totally fair in a socialist society to add bonuses for harder or more dangerous work. What is not compatible is private ownership, not personal ownership of stuff.
The left is primarily not concerned with the wealth disparity caused by different wages between jobs. What drives inequality, which makes our society less democratic and just, is the private ownership of capital (meaning means of production in this context). It would be totally fair in a socialist society to add bonuses for harder or more dangerous work. What is not compatible is private ownership, not personal ownership of stuff.