She does have to aim though. It’s like you’re saying the moment she pushes the button with someone anywhere around her, it locks on. Her reticle has to be close, they’ve even nerfed how far the magnetic cone is so players could escape easier. Again, she’s a healer, not a DPS.
She’s not a tank and she’s not a DPS, her Anti Grasp is literally to deter people and get resource back. She’s not intended for long term fighting. So why should we make it harder for her to do her job when she already has barriers and high mobility heroes to contend with?
Perhaps I was comparing her to the wrong heroes, but still.
I have never had trouble disconnecting her beam unless I was running away in a straight line and never trying to use obstacles.
Maybe try utilizing cover? 
Disengaging is a thing and you can escape her. The only time I’ve ever died to a Moira Anti Grasp is the one time I was Mercy and my team abandoned me so I had nowhere to run in an open area. That was my mistake and partial blame goes to my team mates for abandoning me.
Adding new heroes that can do a singular function another shares =/= nerfing a hero so that there is only one like it. Because if we follow that logic, guess we should be getting rid of Sigma’s and Orisa’s shield because Rein is the OG lord of Shields.