In other words, this is referring to people who in theory, had all of the chops to be a bigger name in the industry but never quite reached the A-list status. They're someone who may have given a great performance in a few movies but never got to the point where they became someone who was highly sought after in the movie industry.

I would have to say the actor that should've been more famous is British actor Martin Freeman and ever since he played Everett Ross in Marvel's Black Panther and then got roles in The Hobbit and the Disney+ series Secret Invasion Martin Freeman should be more famous in America doing more movies. Because Martin Freeman is such a gentleman he could star in romantic comedies and even more action movies in America too