Not that it's a catastrophe or that I'd expect an update, but there's a huuuuuuuuge amount of room for improvement. Heirarchy in the Halo 5 menu is very inconsistent for no apparent reason, and there are lots of instances where you simply can't navigate with buttons that you intuitively should be able to, the most notable example of this being how you can't use both left/right and A/B to navigate horizontal trees.
MCC has some of the same issues. It also has some mind-boggling sillinesses, like when you're navigating down to a level select; it shows the levels below as if you could drop the cursor straight onto them, but when you try to do so, it loads a totally different interface.
tl;dr Spending even a moment in Reach's menus highlights a huge number of things that its successors should do better.