That's not a very good question to ask, because I've already seen it 1,000 times everywhere. So we're kind of beating a dead horse that's already 6 feet into the ground here.
I think looking at it broadly, it isn't a simple yes or no, from a broad consumer spectrum at least. From the developer itself it's a different story.
People have had varying different experiences with the game. The Consumer can determine how much they got for their moneys worth. Me, I was perfectly satisfied with the Campaigns all remastered the way they were. I hardly experienced long wait times and other problems that plagued the Multiplayer. I can't consider it a failure for me when I'm having fun and no problems. I would say that for my experience at least.
Looking through another consumers viewpoint. They have had every problem and bug in the book happen to them. Frustrating times they had. Long wait times, game crashes, problems galore. Their experience has been terrifying. They would consider it a failure, and rightly so, so I wouldn't blame them.
The better question is, does 343 consider it a failure? From a sales standpoint no they shouldn't. But I hardly think they are the kind of company that only considers sales. I can see this from the Sprints where they are making Halo 5. They are putting their heart and soul into the game, and it shows. I don't know if they would ever actually call the MCC a failure outright, but I believe they consider it as such. From apologies to free games for some users, to free maps in Halo 5, they are attempting to make up for it. But that's pretty hard to do when you have a fan-base as volatile as Halo's. The game should have never come out the way they did, and I don't think the free stuff will cut it in the long run.
The best thing that 343 can do is make Halo 5 the exact opposite of the MCC in terms of Stability. The launch of Halo 5 has to go smooth. Nearly every problem that plagued MCC cannot be present in Halo 5. So the one thing need to do is just make a stable game. Will it be enough? Doubt it. MCC turned a lot of people off. It was a harsh blow. But will it mend trust? Maybe. At least that's the best step they can take to doing so.
TL;DR:
Tired of the question
For fans it is varied based on experience
343 should be the ones that consider it a failure, and understand it CANNOT happen again.