Sorry, but "dumbed down" is a negatively-biased way of inaccurately describing the streamlining of a product. If that's what you want to consider it, you're welcome to that opinion. Every iteration of the Civilization series has added or removed different bits; as is true for most products.
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I believe the root of most issues people have with the game are really down to AI and other problem areas, but those are boring to talk about, so it's much easier to try to say "they removed espionage, so Civ V == dumbed down".
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Sigh.
NO. I really don't know how else to say it -- people bring up features from IV because there's simply no other way to explain the concept of "Next Turn Wastelands" -- and for the nonwarmonger -- Civ V has a lot of that.
To the casual gamer, perhaps that's not the case... perhaps - even though they're not really "doing" anything, they're mesmerized by baubles and eye candy. To a veteran Civ player - once you get a look at the eye candy, it ceases to matter much.
To the casual gamer, maybe they're rechecking their tile usage every turn -- unless there's yet another bug I don't know about, V doesn't change your city focus, specialist allocation, or tile usage... so I don't need to do that every turn - only when a new population point hits.
To the casual gamer, maybe they're poring over the tech tree each turn in anticipation of what to research in in 15 turns when they pop the next tech. Few hardcore players need to do that -- tech trees have been pretty much the same since II (and this one is the smallest, IIRC, since I).
It's not "they took X out".
It's "They took things that I used to do each turn,
for example - X from a previous installment, and didn't replace it with anything.... and now -- all I do is either go to war to break the monotony, or, hit Next Turn yet again."