There's nothing wrong with someone getting rich provided they contribute a proportional amount of value to society. Problem is that since the post-WII period (also called the Golden Age of Capitalism) such rewards have been happening less and less [1,2]. In fact, I think reducing inequality is essential for promoting productivity.
[1] https://en.wikipedia.org/wiki/Post%E2%80%93World_War_II_econ...
[2] https://upload.wikimedia.org/wikipedia/commons/7/73/US_produ...