If you "don't know chord progressions" how do you play? By rote? That will get the job done, but in a very limited way.
Chords, scales, riffs etc are all patterns, as are words, phrases and sentences. From graffiti to War and Peace and Bach to the Sex Pistols, patterns are making the communication of ideas possible. The better you are at understanding and employing patterns the better your creativity will be.
