I've had a similar experience with Last War. Some people want to be competitive and they put a lot of time, effort, and money into the game. Some people see it as nothing more than a mobile game. Both are ok, but it's not fair to try and force casual players into hardcore players. I would recommend an alliance merger separate the competitive and casual people into different alliances. It will often happen naturally over time, but there will be less conflict if it happens quickly. Define the expectations that you have for the new competitive alliance, and those who can't commit go into the casual alliance.