I disagree. Season 1-3 were all pretty similar in plot. That could get kinda boring after a while (people that managed to watch all 8 season of 24 need to seriously consider making some life changes). The whole 'never change a winning formula' saying is bull crap. You need to be able to adept and have the guts to try something new once in a while.
I found season 4 of Homeland to be the best, because they were trying something different. I worked out great imo. Hopefully season 5 will be the same. If it's a little less, we just have to swallow that and hope for a better next season. Not everything can be great all the time. I believe the plot lines to be even better now, since they relate to actual world affairs. The writers manage to create bonds between fiction and reality, which is great.
But for dumb people that do not get what's going on in the world, I'm sure it's hard to appreciate these plot lines and grasp them entirely...