Nah, I doubt it was the Arena mode. They just wanted a change to how things worked.
I think it made the game less exciting, and didn't address the biggest thing that they wanted to address. Hard CC is still hecka busted and the game still revolves around it. Reduce chances, bring back stats to reduce the chances even less, make statuses that don't skip turns hit through armor, put in physical resists... and I think you're in a very interesting place.