I think you're completely right about the business drive to prioritize Halo 5 over MCC fixes - and it looks like MCC is the last example i will have of a Halo game I can play with a partner, so i hope they do eventually get it up to snuff. Technical problems aside, MCC seemed like a step back from Halo 4 in its multiplayer application. A jumbled ton of MP options, but not any I particularly want (like just being able to choose one release's MP experience).
Ultimately, though, it doesn't matter much who's to blame for shortcomings in a video game's development - the result is that 343i is releasing, through MS, a Halo title that does not satisfy my requirements for a Halo title. In the face of any announcement of graphical enhancements, video frame rates or other technical 'improvements' the new title will have, it represents a step backward to me and the fans who play like I do. 343i is in charge of which features make it into the game and which do not. Taking well-loved features away from fans for whatever reason, whomever is to blame, is a BAD choice.
Now, if split-screen MP is something that could be added by patch, and 343i were to announce something like that before H5:G's release - I could forget all about it and go on living my gaming life as a Halo fan.