That's a good advice unless "being yourself" sucks. "Be yourself" is non-advice. It can be both good and terrible advice depending on many factors.
Everyone is complex. There are aspects we're comfortable with and others we are not. So you want to improve the latter and stick with the former as long as they work for you, in a sense they help you achieve what you aim for.
Some aspects of yourself aren't really working in some environments so you would just be an idiot to display them while failing to get the results in life you really want to.
> That's a good advice unless "being yourself" sucks. "Be yourself" is non-advice
That's not objective though, "you suck" is entirely subjective, it also depends on context and, in the end, if someone you work with thinks you suck, just talk to them.
> Some aspects of yourself aren't really working in some environments
So change environment, because sooner or later they will show up.
And if you repress them, they will show up amplified.
Everyone is complex. There are aspects we're comfortable with and others we are not. So you want to improve the latter and stick with the former as long as they work for you, in a sense they help you achieve what you aim for.
Some aspects of yourself aren't really working in some environments so you would just be an idiot to display them while failing to get the results in life you really want to.