Major differences don't mean "broken". Halo 4 has its own flows, and its own teamwork, and its own emergent scenarios based upon moment to moment realities, and *not* on timings *built* into the level design.
Jetpack doesn't "break" anything. Halo 4 isn't Halo 3 - its not classic gameplay with static spawns and a level playing field. Choices ARE made in the menus that can provide you an advantage or disadvantage, depending. That happened. Now, given those changes, calling something broken because it doesn't play out like older Halo games makes it seem like people are unable to play the game in front on them, on its own merits.
There are a ton of good gripes here, and Halo 4 needs some changes. But so often here, just saying how Halo 4 is different than old school is the entirety of the point being made in a post. Its those posts I have a problem with, because its not about jetpacks in particular, or flinch in particular, its about how the level playing field has been removed along with some predictability - we know that now - that's implicit. And knowing that, for instance, providing a risk/reward cost to AA usage *is* one good way to provide balance.