I kinda feel the opposite as far as Halo 4 and 5 go. Halo 4's campaign gameplay was okay to me, but the levels felt much smaller than what I'd grown accustomed to with 3, ODST, and Reach, so that hampered my enjoyment of it. Still, I admire a lot about the game. The sound design for the guns was pretty solid (I'm especially fond of the DMR in this), the art design was absolutely stellar (I'm sure this would be a point of contention since Halo 4 marked a shift from a industrial and gritty-tinged sci-fi art style to something more high tech and elaborate in its design, but I really love a lot of the stuff in it), the Halo 4 score, while pretty different from the previous games', still had some pretty epic tracks, and the actual story and the way they handled Chief and Cortana's relationship was really evocative.
And as far as Halo 5's campaign gameplay goes, I thought it was a big step up from Halo 4, containing bigger, more elaborate levels, a fair share of vehicle sections that didn't feel on-rails, and really big battles replete with tons of enemies and particles flying everywhere that just look great on an Xbox One X. Of course, I had my gripes with this one as well, such as the storyline not being all that satisfying in how it plays out, if you're playing Solo, the team AI isn't great, although I do appreciate how complex they tried to make their routines, the Kraken fight was unfortunately pretty dull, and although the very stable 60 FPS was appreciated, it felt like they sacrificed too much in graphical fidelity, giving the game a look I almost want to call cartoony.
My totally amateurish opinion is that 343 is a very talented studio that has some massive shoes to fill, but they haven't found their footing yet, and perhaps they're trying too much do their own thing yet feel like a Halo game AND please a very ardent fanbase.
My useless suggestion to these foos, take the evocative storyline from Halo 4, mix it in with the more open ended gameplay of 5, make it M rated and give the art design a bit of a gritty sheen, take a page from Modern Warfare 2019's sound design, and maybe y'all got a stew goin'.
Fuck, didn't intend to ramble on this much.