CI isn't anywhere near poor enough to be considered the worst wonder. The extra defense buys time to reinforce against a SOD. It's on a standard tech path (unlike, say, the SE). Denying it to the AI is useful, whereas you actively want the AI to build some wonders (e.g. the Hagia Sophia, maybe the AP unless you're cheesing it). Finally, it's one of the few stone wonders that appears during the time period, which is good for fail-gold, if nothing else. The Hanging Gardens can also be failed at about the same time, but you need to build an aqueduct first and the AI tends to bee-line mathematics en masse anyway.
No, it's not good, but we're dealing with superlatives here. The SE is the worst to build, followed (at some distance) by the Hagia Sophia.
No, it's not good, but we're dealing with superlatives here. The SE is the worst to build, followed (at some distance) by the Hagia Sophia.