The phrase "it has become a commonplace" is correct and can be used in written English. You can use this phrase to describe when something has become ordinary or accepted. For example, "In today's world, the internet has become a commonplace."
It has become a commonplace situation: a corporation threatens to move its headquarters out of New York City.
It has become a commonplace to acknowledge that a post-war Afghanistan will "not be Switzerland".
It has become a commonplace of leftwing thought that the New Labour governments were "neoliberal".
It has become a commonplace nowadays that "utopian" is just a polite way of saying "totalitarian".
It has become a commonplace here in Brazil that we are an optimistic people.
It has become a commonplace (one that I've also relied on) to call the movie a screed against bourgeois life.
I had been involved in the early development of optical coherence tomography (OCT) in the early 1990s, and by the time I came to Duke a decade later, it had become a commonplace diagnostic technology in ophthalmology.
However, it had become a commonplace by the beginning of the 21st century.
This critique has become a commonplace — it's at the heart of Gary Weiss's piece on Geithner in the new issue of Portfolio, where Geithner is described as "tentative," "lacking in boldness and imagination," and lacking "fresh ideas".
It has become an instant commonplace to assimilate the movie to the "overgrown man-child" genre, but there's a reason why such films are made: such things happen, promising individuals have trouble getting on track in the transition from school to world, parents have trouble compelling their adult children to help themselves, and days and weeks slip unawares into years.
Fire had become a commonplace.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union