Before you say "but end turns!" let me remind you that getting 3100

is not easy. And neither is keeping the tech pace for unlocking these buildings.
And there are at least 3 different ways to handle culture gains! Unlike in CIV4 in which you had only one option: religion. Okay, maybe two: religion + science or religion + espionage.
let me remind you that getting 3100

and "pressing end turn" are related
culture in civ4(continued list):
Okay, maybe three: religion + culture slider + science(to unlock new culture stuff)
damn forgot one! ->
Great Artist
damn! another one!
artist specialists
o no! civics! (Caste System, Free Speech, etc.)
and wonders! particularly the Sistine Chapel( +culture to every specialist)
The reason why you find it boring is because there's no (or little) "instant buttons of happiness" like whipping, switching civics, drafting, building units every turn etc. Whatever you do in CIV5 takes 5-15 turns to take effect.
that's called a constant stream of rewards
games lacking such stream(e.g. rewards are far apart in time/space) always have stretches of playing time, where the player must force himself to go on. this effect happens because the "effect" of the last reward wore off and the next reward is not close enough.
That period of wait for an effect to take hold isn't popular by today's schizophrenic players who feel severe anxiety if their PC takes longer than 15 seconds to boot, or a webpage takes more than 2 seconds to display.
time between turns of a minute or more is
unacceptable.
for me watching the game play itself is
not fun.
A perfect example would be massive moaning on how happiness in this game is a problem when having a large amount of cities (lets say 10). Building a colliseum in each would take, say 15 turns at an early age, but would provide 40 extra happiness (and unlocking the circus maximus for 5 more).
what you mentioned is called punishing the player for success(you would call "winning a war" a success?).
that's simply bad design, especially in the light of the fact that the game was aimed at the casual crowd.
Nothing prevents anyone from investing into new happiness buildings 10 turns before an invasion (to prevent plummets into severe unhappy), but nobody is willing to delay their conquest by 10 turns -- that's preposterous!
what about AI's rage quits?
decline the reward for winning or suffer?
If you look at players' complains about CIV4, I'm sure you'll find many reasons why CIV5 was built in the way it was.
exactly

especially the "insult the player diplo feature" when an AI pops in diplo and says something negative about my civ. fun stuff!
on topic of streamlining
i have little understanding of what is meant by
streamlining. what i think it means is removing tedious and/or repetitive tasks.
a prime example:
since all merchant/artist/engineer/science specialists are essentially the same, why not unite them into one slider per type?
this issue will rise in any mod that has lots of buildings with specialist slots. right now this problem results in lots of scrolling and lots of clicking
