Would it help with your diplomatic resource constraints to attack larger nations? It takes as many diplomats to DOW Russia as Hedjaz, after all......
It does indeed, but adding more war goals also costs diplomats. There no point in fighting a twenty state GP and only claiming one state. That's just too much work, and it resets the truce, which could give time problems with both GB and Russia if you don't start early enough. I'm sure that's why war with GB is up now.