Who knows what really happened? Maybe Pietro was always meant to die in AoU. Maybe not. I just happen to think the FOX/Disney war had something to do with it. Maybe Feige and Whedon dislike Quicksilver as a character and wanted him gone. I tend to think this is NOT the case because Feige and Whedon have mentioned how they were "twins fans" reading the comics growing up. I sure wish Agatha could have "hate taught" Wanda some more. Despite her excellent skin regimen, she's in essence a filthy old hag who has lived for several hundred years. If she explained some "rules" about chaos magic, it might have cleared things up. Like maybe Wanda could only tap into a certain amount of magical energy and couldn't create more than five "constructs" at a time or whatever. I don't care what the "rules" are, and they don't have to be explained to me. Just as long as they're applied REASONABLY consistently, I'm fine. I complained LOUDLY on the WandaVision thread that Hahn practically disappeared for a few episodes (this happened to a lesser extent to Bettany). Hahn stated that she was Salieri and Wanda was Mozart. If viewers could have seen Agatha grow jealous and hateful of Wanda throughout the show, I think that would have solved her "motivation" problem. I would have bought the idea that Agatha believed Wanda was unworthy of her powers and thought she had the right to take them. I think Agatha could have explained the extents and limitations of Wanda's powers more because she's in an excellent position to know about that ****. I also happen to think that the whole Fietro subplot distracted from the Wanda/Vision conflict in Episode 5. I was worried about that happening at the time and I was disappointed with the direction WandaVision took after that. The two of them should have reconciled more naturally than they did in my opinion.
We talk about the costs of magic a lot. I would have actually incorporated Strange's more recent history from the comics for WandaVision. Not saying Wanda should puke before every time she casts a spell, but by creating Vision and the kids, I think it should have taken a physical, mental and emotional toll on her. The people of Westview wouldn't have to be mentally enslaved. And after a while Vision and the boys should have convinced her to let them go to restore her health or something. I actually thought the show originally was gonna do something like that.