Anything formulaic follows a formula or pattern, especially in a mechanical, by-the-numbers way. A formulaic TV show is predictable and probably similar to lots of other shows.
Have you ever noticed how many songs are similar to others? When a song is almost identical to previous songs and it’s not very original at all, it's formulaic. This word usually conveys a lack of imagination. If you call a movie formulaic, you're saying it's so much like other movies that it probably didn't need to be made. A formulaic speech follows a pattern that's been used many times before. The opposite of formulaic is original.