You guys will defend no matter what... Apple messed up, this feature was announced almost a year ago. If it still needs this much work, they should have never announced it in the original iOS 11 keynote.
Agree, they shouldn't announce features that aren't ready to ship that day. I really miss the old days when Steve would say "available today" or "pre-order today, available on Friday."
However, this massive delay makes me think there was some intervening event we aren't privy to. For example, Apple has been really harping about the whole security thing. What if in September an engineer found an exploit that could compromise all iMessages in the cloud messages? What if the exploit wasn't something that could be easily patched, and required a proper "back to the drawing board" approach?