Hey there, and welcome to the Forum.
Personally I enjoy that the difficulty level is displayed in a color scale, that goes blue, green, yellow (all easily solvable if the right troops are picked), then orange and red (pretty much cater or go home).
I learned a very harsh lesson in the summer of 2016, by trying to reach my mentor's city. This was back before the color scale was available. He said to fight, not cater, wait until my troops were strong enough. Ah me, good times. But I would have been better able to judge that under the color scale system, than trial and error.