Plebcore is a large genre of music for the common hipster who often lacks taste in what is actually good music to the average commoner. "Pleb" is short for "plebeian". So Plebcore is a genre of music for someone who is not a real music fan. Often times a hipster likes Plebcore because the music has low popularity and the artist is likely to remain independent and/or unsigned.
Real dubstep is plebcore while what many consider good dubstep is just filthy brostep.