The complaint is the same as with Imagine Dragons. People hate them because they are mass production, generic studio music. No musical genius, just basically proven formulae to make music that will sell well. You can find some websites where they overlap music by different artists that match almost exactly. Same rhythm, key signature, chord progressions, etc. A lot of mainstream music is just rinsed and polished repeats. Even if they didn’t base it off some other work, it’s still following simple writing techniques and then adding in synthesizers and auto-tuners to make people sound good.
I’m not an expert in this area, but that’s the basic idea of mainstream music. That all being said, I still appreciate catchy music that can get you into a groove.
