but i think Retreater has a point , AoA IMHO was not design very well... the devs struggles with the idea of introducing the world Golarion and the new rules... and the AP ended being extremely railtoad and very hard (bad design for me) ...I'm going to be blunt, I think your group was the problem with your group, and you're kind of scapegoating the system. Do you really think its the system's fault your players are 'hating each other?' if it was that severe wouldn't it be time to revisit their demand you run it exactly as written and accept you'd all have more fun with slightly adjusted encounters?
If they don't want to get better, and they don't want you to make it easier, and they're getting angry about it all the same, and then take it out on each other, they sound like jaw-droppingly immature people. As a GM I'm kind of secondhand upset they put you through that, and would have slapped them down hard. For point of reference, I went through something similar with a 5e group, and then went on to enjoy the system more with other people entirely after leaving that group.
Any game is garbage with toxic people, and if all it takes is a hard game to bring out the worst in them... then yeah, def toxic people.