I've actually been meaning to talk about this for a while. Its not that CE's armor is out of place, it's what we've all collectively decided Mark IV looks like.
Bungie originally designed the Mark IV in the first photo, but this was all we had to go off of until Halo Wars.
I've always personally thought that the Orion armor (The Macworld 1999 Armor) would have made for a good canon Mark IV, considering it literally predated the Halo CE Mark V design.
During the making of Halo Wars, the last two photos were concepted. It's far closer to the Mark V in design principles, however for the sake of fitting in an RTS and being easily recognizable from a birds-eye view, they went with what we know now as the Mark IV. Broad shoulders, muscular armor and solid vambraces and grieves similar to Halo 3's Mark VI. I can assume this was done to make it more visually recognizable as Halo, especially off the back of Halo 3.
The problem is, that design looks more advanced than the Mark V, almost like it should have been a Mark VII and came after Halo 3, not way before. It looks like a design evolution of the Mark VI, and yet it was cool enough and iconic enough to be used forever more as the visual representation of the Mark IV.
Part of this blame can absolutely be laid on 343i, deciding to go with a clearly exaggerated and anachronistic design from an RTS and making that canon. Part of it the blame is simply that the Halo Wars design rocks, it's really cool looking, it just should never have been the canon Mark IV.
The Mark IV should have been more like the early concepts, bungie's old blueprint, or the macworld armor. It should have shared the same design principles as the Mark V, but in a rougher, earlier form. CE's new remake has decided to go with a strange combination of the anime Legends design crossed with the body of Halo Wars, and I can't fault them. The damage has already been done after all.
This isn't Campain Evolved's fault but I've always thought the in-universe design evolution of these armors makes no sense. CE's armor feels so out of place