There are so many things they need to do to make the game more attractive to new players, and to lose fewer old players to frustration, but that would be a huge list. This move would clearly be unnecessary if they had a large and growing player base.
To increase war participation, they need to improve the rewards a lot. For tough wars, any atomic attacker is facing a net loss of oil unless attacks go perfectly, given planes, generals and factory troops. The rubies earned in a war barely cover troop card costs, assuming you use marco when he actually brings troop chests. They tried doubling the rewards for a week once, and it was much better and more appropriate, especially for the top few ages.
I suggest they add a way for an alliance to do multiple wars at once (each player can only be in one), and then limit the war sizes to 5, 10 or 20 players. Keep 3-4 wars running at a time with different groups of players, everyone is active and involved, and there are far more matchups out there, so easier to find a good one.
