The old joke in the Soviet Union was to the effect that the workers pretended to work, and the bosses pretended to pay them. That’s the inevitable result of creating a system with minimal material incentives for excellence. It’s a problem that socialist societies never solved.
Of course, people work for reasons other than material rewards, and systems with too much inequality tend to be politically and economically unstable, so there are arguments in the other direction, as well. It’s a balancing act, and different countries handle it differently. The United States tolerates more inequality in exchange for more dynamism than, say, Denmark. It’s a spectrum, not a black and white issue, and where you stand on it probably dictates the way you vote.