Some people don't understand the difference between streamlining and dumbing down, and assume that it's an affront to your intelligence if you don't have to spend months learning the mechanics of the various game systems.
Ain't that the damn truth. to be fair, the Civ series has never been a particularly impenetrable one, certainly not like many turn-based strategy games of days gone by, but that doesn't mean that it couldn't benefit from some streamlining. For me, Civ 5 (what little I have played it anyway) is more "different" than dumbed-down. I can see how some of the bigger departures from the Civ formula could be considered change for the worse by some fans of the previous games (particularly Civ 4), but that dislike is not indicative of a "dumber" game. I'm thinking it just means the changes weren't to your liking.
“The greatness of a nation and its moral progress can be judged by the way its animals are treated.” - Mahatma Gandhi