Given the state of the game as seen in the Showcase Demo, this is a very justifiable delay. Quite apparently, the current fidelity of the product is well below consumer expectations, and there was a lot of concern about whether or not 343i had adequately accepted the negative feedback and had appropriate answers at hand to implement before launch. In short, I guess they finally are taking the feedback appropriately, and they didn't have plans or fixes for the problems to realistically put in place before the planned holiday launch.
What's extremely disheartening (and a bit relieving simultaneously) to me about this is that it is an implicit admission that the game isn't done- in fact, that it isn't even especially *close* to done. At the tail end of a five year dev cycle, they have only this to show for. That's seriously discouraging, and it makes 343i look pretty inept given the immensity of the time and budget they've had at their disposal in getting this franchise back on track since Halo 5's undeniably underwhelming debut. That's coming from someone who earnestly tries to keep their head on straight in the Pro/Anti 343i argument by heaping them credit where I see that it's due.
In this case, the only credit I can think of for them is that they had the nerves to delay the game, knowing full well how it would make them look, because it needed to be delayed (insert tired Miyamoto quote). There aren't very many exceptionally good excuses for what could have kept a team like 343i from delivering a complete and polished product with a five year development window, new engine or otherwise. Many other devs in the gaming industry at-large, let alone the former stewards of the Halo franchise itself, have done a lot more with a lot less time and money.
Given the issues, I'll again say that I do believe delaying was the only appropriate move at this point in time. But that doesn't alleviate the staggering, eyebrow-raising question of how it took five years for 343i to deliver what we saw at that Showcase. That speaks to a very disappointing lack of direction and drive in the development process, which in conjunction with the delay itself means that the hole of bad vibes 343i has dug themselves into is going to require a seriously impressive Halo experience to redeem them.
With the delay on top of all the other problems, "good enough," simply won't be good enough. Here's hoping they're sitting on something truly remarkable that just needed a bit more spit and shine. If they delay it just for it to be fair to middling? That'll be an insane waste of everyone's time, attention, and money on both the development and consumer side of the equation.
Get it together, 343i, please. I hope mine and everyone else's misgivings about your competence are proven very, very wrong when we (eventually) get Infinite in our hands. In the meantime, you can stand to benefit from some tough love and constructive criticism from fans who've been waiting patiently and rooting for you since Halo 5 and ridden out this polarizing decade of your stewardship of the franchise.