Depends on what we mean by egos. In the modern game of millionaire celebrities every established player could regard himself as a star. All Star teams do not necessarily have problems and if we look to the movie industry ensemble films can have several lead actors.
If a player thinks he’s better than he is, then its a problem in every warp of life. For United we’ve had those players in abundance.
If the player with ego thinks he’s above criticism, then thats something for the manager to deal with, and if he can’t the manager (or player) won’t be staying long.
The problem in my view is when a young player with ego (based on performance) conflicts with the senior player(s) whose ego is based on past performance and seniority. George Best and declining Bobby Charlton spring to mind.
Really the manager should consider working partnerships across the field eg center defense duo, midfield duo, attacking duo. The players must work together as equals. And if they can’t ……. well one has to go.
I wonder what prompted your post. Zlatan and Sweden possibly?