That kind of ignorance is going to be their downfall anyway. You could “know every song” but you still need to hear how two of those tunes are going to mix, at the very least you have to beat match them (unless they use the sync button). Without those essential skills, they’re only going to spectacularly fall flat on their faces with their mismatched phrases and off-beats
I’m still a bedroom DJ but I always make it a habit to scroll through a track and hear how it’ll match harmonically with the current song before fading it in; so there are those out there that still take the craft seriously its just the shortcuts in digital DJing are making success too easy with minimal work. Once the work and pressure that they’re not prepared for sets in, they’ll crack under it.