Why is Cassiopeia considered challenging?
I was considering picking up Cassiopeia since apparently she's meta now. I'd like to know, why is she considered really challenging? Judging by her moveset the only things that stands out to me as particularly difficult is that you need to drop a weirdly-shaped cloud of poison in order to lock down champions that are already slippery and that her ultimate works best when people are facing you, despite there being no turn rates.
From my perspective, she looks like a reasonably basic mage to just pick up and play, and has a lot of counterpick potential with her mobility impairment. She just has a high skill ceiling due to her ultimate and w. Am I reading this right?
my hands get tired because of constant need to move, press E and Q, also be ready to use flash.
Because of the nature of her damage she always needs to move around teamfight, in the same time hitting Q and pressing E almost everytime

and
to stay relevant. Where as some champs only need 2 items to feel complete.