Except for Halo 3: ODST. So is that not a Halo game, then? As well, the Campaign is still linear. You won’t complete The Command Spire before completing The Tower.
Except for, again, Halo 3: ODST and the various Virgil Caches that would get progressively better weapons and vehicles the more Audio Logs you collected.
Except for UNSC ammo crates in Halo Reach, Halo 4, and Halo 5.
Except for the Needler, Carbine, Brute Shot, Fuel Rod Gun, Mauler, Concussion Rifle, Boltshot, Suppressor, Scattershot, Lightrifle, Incineration Cannon, Binary Rifle, and Plasma Caster.
I must have missed where we weren’t taken to a “cool sci-fi location”, being on the oldest Halo ring of them all.
Halo: CE had one location: Installation 04.
Halo 3: ODST had one location: New Mombasa, Earth.
Halo Reach had one location: Reach. And both Reach and New Mombasa weren’t particularly “sci-fi”.
Halo: Fireteam Raven had one location: Installation 04.
So are these not Halo games either? Halo Infinite has taken us to an interesting and sci-fi location. In fact, it’s the first FPS for us to be on a Halo ring since Halo 3. The problem is you’re not interested. Ergo it’s a you problem.
Halo Infinite factually has a story. Your opinions on that story don’t matter; it’s there. Brutal and dark on part of humanity? Let’s see: within the first three seconds - literally - the UNSC Infinity is critically damaged, possibly destroyed, and the Chief is brutally defeated and left for dead. Crash landing on Installation 07, the surviving UNSC forces are forced to hold out for six months, stranded from all other UNSC forces - what remain - and surrounded by the Banished. HIGHCOMM is destroyed. Laconia Station is destroyed. Even with everything done in Infinite’s campaign, the UNSC is not in a good position. That’s pretty damn dark.
And to the Covenant, it is. Did you pay attention to where it was stated that those are in place - storyline-wise - to demoralize the UNSC forces? Never mind that the Grunts have pretty much always made jokes and comedic humor comments. Talking about Nipple Academy and how they’re calling dibs on Chief’s helmet, or wishing for Rukt’s Fist for Christmas. Unggoy got more serious in Halo Reach through Halo 5, but fans wanted the goofy Grunts back, didn’t they? Well, here they are again. That is, in fact, the “usual Halo game atmosphere”.
Again, this is a personal issue. You seem to be ignoring the storyline entirely, focusing on gameplay elements as though they are proof against it. In much the same manner of thought, were we struggling in Halo: CE? I know it said we were always on the run, and that the Covenant was winning, but there sure was a lot of UNSC stuff conveniently around. Were we still struggling in Halo 3? Defeating the Covenant and the Flood sure seemed easy as pie…