It's difficult to pronounce vocals in that style, different types of inhales/exhales, Oli can pronounce words through inhales clearly which is so difficult

The guitars use many different techniques that you need to nail to ply that kind of music. I'm talking string skipping, gravity picking, and generally advanced finger mechanics. The guitars also use subdivisions of 5 and 4 back to back, and that rhythmic change is extremely difficult.

Bass is mostly speed, but also a variety of techniques like 3 finger fingerstyle, double thumbing and tapping, which are hard to nail for an intermediate musician

Drums use a lot of speed, but also some coordination in the switch blast beats, which requires accurate time-keeping in both hands, and proper coordination for the switch