Oh, there are enough people who want intellectually challenging games, but there are more people who just want to move little colorful figures around.
There is a snarky saying about television that might apply to computer games now. See, in the beginning, clever people made television for other clever people. Then, the bosses realized that there were more non-clever people than clever people, so the clever people began making television for non-clever people. After a while, the clever people got disgusted with that and left for other things. Now we have non-clever people making television for other non-clever people -- a world in which Firefly and Veronica Mars get cancelled, and (with the possible exception of Fringe) most of everything is simply mindless trash.
For a long time, computer games were made by clever people for clever people. My feeling is that we are now entering the phase where clever people are making games for non-clever people -- where mindless console games and FarmVille are the norm, and complex PC/Mac games such as Civ IV are rare and far apart.
If you think this is bad, wait for phase three.
I don't think it has anything to do with the word "clever".
"Clever" has no international measurement... or there is no absolute way to judge who is clever and who is not. Normally, everyone think he himself is clever (that include the fools) and if he dare to state that openly, everyone else will think he is not.
The actual problem is we are having two different Civ designers with very different personal character, that is the main reason why Civ4 and Civ5 can be that different.
Civ4 designer makes Civ4 features rich. But he has his problem. Let me quote 2 BTS examples:
1. Gunship
a) its amphibious ability has been removed
b) it can't capture a worker (instead it always destroy one if you place it on the same tile of an enemy worker).
Anyone can argue a) is for game balancing such that the gunship unit is not too powerful, but I doubt anyone can give me a reason why b), it simply make no sense.
2. You can build mine, cottage in neutral zone tiles, but you can't build farm. Ridiculous, is the word isn't it?
I dare to conclude, Civ4 designer is one who like to torture himself for no apparent reasons, thus when he designs Civ4, he extend that to all his players. There are many more small restrictions like above that really don't make sense. (they are merely there to cut your fun of playing Civ4)
I agree to the claim that Civ4 is feature rich, but I can't agree it offers more choices. (at least I dare to say most of the choices are not interesting, spoiled by brainless, unnecessary restriction)
I think Civ5 designer happen to be just opposite with the former.
In a way, I like his decision that if something is allowed in the game, he allows you to do it to its extreme. For example, he wants to let you cross the water, so save the trouble of building ship, just cross it... every unit is now a transformer.
I mean he is either a guy with true guts or he has been forced to design Civ5 with fewer features as a prerequisite. I suppose he already foresee a huge protest on the release of Civ5, that is the reason why, we can't even see much details of Civ5, even in the last week before Civ5 is released.