In order to capture cities now, you need strong melee units or siege units. There's just one problem: strong melee units means swords/longswords, and siege units means catapults/trebuchets. All of those units require iron. What happens if you don't have iron? Currently, the answer appears to be "you are screwed", and enemy cities can only be taken with very heavy losses using non-iron units. This is not an example of good design.

Unhappiness is now global, since your population always contributes to unhappiness, but the buildings that fight unhappiness work locally. Also, while a colosseum is limited in how much happiness it can provide by the local city, wonders are unaffected by this rule, as are luxury resources. Uh huh. When you need to start bending the rules like that to cover up mistakes, I'd say it's a sign of shoddy design work.