I don't think I've ever seen an OST break a show, but they can sometimes make the show, or at least make the show that much better. Whether the songs are simply just catchy and get stuck in our heads without any sort of permission (ALMOST PAAARADISE!!!!) or if they are super good songs that stick with you and end up in your playlists and purchased items, OSTs are a major part of a drama. That kiss scene would just not be as good without the swelling love ballad in the background increasing the feels by at least 100%.
Or they can add an additional bit of humor when used at just the right moment:
Here are some of the Korean Drama OSTs that have moved me the most, that have definitely made it into my collection, and are constantly being sung and played by me all.the.time...
