probably because it requires no skill to you
The skill lies in the timing. If the hack is not well timed you basically wasted a cooldown because in most situations, youre not gonna be allowed to follow up on it yourself. So making sure your teammates are in position and the enemy has little escape options is where the good hack differ from the bad hack.
is risk free since she can just teleport away
Ever since they made translocator destructable by chip dmg, you cant afford to set up near a fight to increase up time. Which makes every translocate basically a soft reset, which removes you from the fight and makes her team fight a 5v6 for a decent amount of time. Thats everything but risk free. She might not die, but she isnt helping her team to win either.
can’t be predicted since she’s invisible before hand
I’m sorry but thats a view point from someone who doesnt like to pay attention and has no interest on working on their situational awareness. Based on health pack locations and the map structure, there are only so many viable places from where she can pop up from because she cant afford to be seen under any circumstances if she wants to get a hack off. And its not just the hacked target which is not allowed to see her, its the whole enemy team. Look for high ground places around you and chance are shes coming from there. If she decides to come from behind on low ground, she has a) worse angles to go for the target she needs and b) less cover after being exposed which goes back to her being forced to translocate away and missing in the hack follow up.
is fast enough that you can’t really do much to react,
There are plenty of people who react to it even at average ranks. That can only become better as you climb higher. Unless you mean you cant react consistently. But if that were the case she consistently would never get a hack off.