This is bad. Like, BAD. I do not comment often and do think people have a tendency to overreact to game developer changes, but this is just plain disgusting. Assault battles are a motivation for many, as they are a challenging event that provides good and regular rewards if you manage to finally beat them. By reducing their cadence (with the obvious end goal of facing out all “old” assault battles) you are literally removing a reason people farm different teams - you are removing reasons to play your game.
This change is harmful to all players, removing a challenge, a reason to progress and build different teams, and a source of rewards, but is especially harmful to new players, who are already faced with many hurdles and already feel lightyears behind the end- or even mid-game players. New players that are essential in making sure your game - your source of income, if you haven’t forgotten - doesn’t disappear.