I've explained it a lot, but since I like listening to myself.
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Stacks or not was never a big deal to me. I never liked the RNG factor though.. But I only play single player so in the end it just translates to "dumb ai suicides army"
Of course the whole suicide a stack of catapults thing all the time is hardly accurate either since using a few smaller stacks of mounted units was more efficient plus horse units could hit multiple siege units too.
I think the game did a good job of doing peace vs war. There were more reasons to not kill each other and things like Free Religion incentivized getting more religions and it didn't have to be competitive.
It also made you take sides. Being neutral was a great way of being attacked by everyone so you had to balance it out.
So for those that don't like war there are many options. But of course killing everyone works too.
Also the game isn't that micro intensive thanks to the number of auto governor options, even for buildings. I mean sure it was needed to optimize on high levels but games can go faster.
I wouldn't say it is untouchable (balance is not that good) but it did a lot of things right and its flaws are less apparent.
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The thing in Civ 4 is that you could do a lot of different things and still feel like you're not gimping yourself yet the game is still harder to master.
The other thing is that you didn't have to do tedious micromanaging if you didn't want to. Despite allegedly being more "streamlined", 5 and 6 fail miserably in this department.
Also wonders were cool.
I mean, it's hardly perfect. Balance is terrible and that's hilariously pathetic when you remember there's not much difference between civs. Civ 6 actually seems to be relatively well balanced if you take out the outliers as there aren't really many civs that I would consider purely useless-- less than a handful. There's also huge RNG luck factors in combat and it also shares 6's problems with forward settling and bad maps too. But it's still much easier to pick up...
I like 6, but due to the numerous UI flaws and pointless endgame mini-tasks, the difference is evident. Take this recent game of IV which ended on turn 378. It ends in under 3 hours and I left it running for a bit near the end too.
Oh yea, Egypt is good in this game. Used to be my favorite civ. They were cool in 5, and then well....
Now note that it was very rusty since I could finish games much faster than this. Now, if I were to close on a turn 400 Civ 6 game, how long would that take?
Of course, there is no timer in 6. :S
Overall? Actually playing Civ 4 reminds me of the stupid design decisions they made-- well, in fact, my avatar is of the Apostolic Palace which is one of the worst design decisions I have seen in the franchise. Well, up there with warmunger penalties. But hey, regardless of its issues it was still fun, and I can still say the same about Civ 6. I've always been about what a game does, not what a game doesn't.