From the Urban Dictionary, "empty suit" is defined as follows:
Someone puffed up with his own importance but really having little effect on the lives of others. It is often used as an insult to disparage others who really don’t deserve the title. The true empty suit, which conjures up the image of a business suit of clothing without a person, really doesn’t know what he or she is doing. He or she is ineffectual, perhaps a phony, and is about as relevant or helpful as a suit hanging on a rack.
To call someone an empty suit implies that you think they are a complete waste of time. Editorials on politicians love to use the term empty suit to describe people seeking presidential office. This or that politician is just “an empty suit,” to quote the words of numerous political critics, and is thus undeserving of our attention.
Some politicians do deserve the title. A senator with a very poor voting record, or failure to attend senate sessions could clearly be called an empty suit because he is not really performing the job for which he was elected. On the other hand, some politicians may advertise themselves as “not just an empty suit” in order to distinguish themselves from their implied empty suit peers.
Barack Obama is a real empty suit. He's never accomplished anything of importance as a politician, yet he earns the praise of millions of United States citizens.
Well dressed but shallow or ineffective people, particularly in the context of higher level male corporate employees or executives.
Example: That dickhead can't decide anything... he is such an empty suit.
From investopedia, "empty suit" refers to:
Someone who is high up in a company due to unfair hiring practices, such as nepotism, and doesn't really do anything for the company. It could also refer to someone who makes themselves out to be much more able or important than they really are. Generally, the term is used to describe someone who is not particularly good at their job.
Empty suits can be found in many large organizations. Incompetent employees who know how to work the system can climb into positions of authority that they really don't deserve or aren't able to maintain effectively. Some consider governmental positions to be commonly filled by empty suits that were appointed for political reasons.