You will never be criticized by someone who is doing more than you. You will only be criticized by someone doing less.

I am not sure who is the author of this quote, it is attributed to Denzel Washington, but also Nipsey Hussle, and might be none of them.

You will never be criticized by someone who is doing more than you. You will only be criticized by someone doing less.

The meaning is straight forward, people that work harder than you will not criticize you, it is only the ones doing less or nothing.
There is a truth to this even if you switch verbs.
Like :
You will never be criticized by someone who is doing more than you. You will only be criticized by someone doing less.
You will never be criticized by someone working harder than you. You will only be criticized by someone working less.
You will never be criticized by someone achieving more than you. You will only be criticized by someone achieving less.

The general truth here, is that people who do, criticize others rarely, because they know that the road to achieving a goal takes time, and that each person makes mistakes, and learn from own mistakes. However, people who usually do little to nothing, behave like experts and think they are geniuses, thus distributing advice left and right.

I will quote some ideas presented by others as possible explanation of this quote:

when people are failing themselves, instead of owning their own inadequacy and improving themselves, they instead hide behind a mask. One such tool they use is to discredit others and point out the flaws in other people.

The one who is doing more than you is in a better position to understand your drawbacks & instead of criticizing your drawbacks, he will appreciate your good points & also help you come out of your negative complex. Whereas someone doing less than you is carrying a complex that he can never equal you or go above you, as he does not find ways & means to surpass you & the only alternative left with him is to criticize you.

those who are successful often didn’t start that way and they were criticized along the way too and they don’t want to cause that same pain to others. I’ve also found people who are doing well in life tend to be more open minded. You have to be too reach a certain level of success, therefore those people won’t judge you based on where you are in life now.

People who have been through the struggle of repeatedly accomplishing difficult things understand the plight of those who are making a genuine effort at it, or who are taking risks to achieve their dreams. People who did nothing to pursue their own life’s passions are often quick to criticize those who even dare to try. Misery loves company.