Because the shit that's popular today are pop and rap songs that use the same repetitive beats, a FUCK TON of autotune that makes it hard to tell if the singer has any semblance of talent or not (I usually assume they don't if they need to use THAT MUCH autotune and vocal effects and they're just masking the fact that they can't sing/have no talent and are just compensating by making themselves sound like robots) and lyrics about sex, love, heartbreak, murder, doing drugs, money, valuing material possessions (cars, money, etc.), bragging about how rich they are and rubbing it in everyone's face, etc. Metal is only being kept alive by underground bands and older bands (Metallica, Megadeth, etc.) that are still making music/touring (but longtime fans will say they fell off, sold out, aren't good anymore, washed up)