While I generally agree with your point, I disagree with 50 Shades as an example; I'm not familiar with the girl, but Jamie Dornan is a pretty solid actor starring in a moderately known TV series (The Fall, with Gillian Anderson from The X-Files and Hannibal; he plays the antagonist) and does so exceedingly well. He was also on Once Upon A Time, another relatively well-known TV series.
There's just tons of actors we don't recognize as superstars who have an established career with prominent roles that we're not very aware of. My ex would often pause whatever we were watching on Netflix to check quickly on IMDB if some character was X character from X show, and she was generally right. With time, I realized we were often watching a bunch of really good actors in a ton of stuff that I wouldn't have noticed if not for her.