It looks like 343i have made the appropriate changes to the art direction for Halo: Infinite after the disasters that were Halo 4 and 5. Although, hopefully they drastically improve the lighting and textures before release. What hasn’t changed is the gameplay. Halo: Infinite’s gameplay is, at its core, exactly the same as what we got in Halo 5.
Sprint
Many Halo fans were unhappy with Bungie when they introduced Sprint in Halo: Reach. 343i turned it into a base mechanic for Halo 4 and 5, making it a core part of the gameplay. This was not what fans expect or desire in a Halo game. (There are plenty of videos explaining the flaws of adding Sprint to a Halo game on YouTube - See ChrisRayGun, Favyn, LateNightGaming and more.) When fans desperately pleaded with 343i to remove Sprint after Halo 5, it seems they ignored their fanbase completely. Sprint has returned. And jeez, what did they do to base movement? Did we not want faster base movement? Why is it even slower?
ADS
Halo 5 copied-and-pasted the mechanic of ADS from other FPS games. 343i altered the visuals slightly and renamed it Smart-Scope, but at the end of the day, it still very much functions the same as ADS in these other games. The Halo: Infinite demo has shown us that ADS will indeed be returning. Whether it returns for every weapon or just some is yet to be seen. Either way, like Sprint, it’s another mechanic from outside of Halo that was added to Halo 5 and appears to be staying in spite of what the fanbase has proven they prefer.
Grappling Hook
Whether the grappling hook is an Armour Ability (like in Halo: Reach and Halo 4) or Spartan Ability (like in Halo 5) it belongs to a category of ‘abilities’ that fans have been asking to have removed every since the release of Halo: Reach. Changing a thruster pack or jetpack to a grappling hook doesn’t disguise the fact that it’s supposed to be ‘advanced mobility’. All it does it change these abilities into something that looks less like it belongs in a Halo game. Essentially, these abilities are returning but in an even less desired form.
Hit Markers, Non-Skippable Animations (i.e. when pressing a switch), Bloom, Slide, Clamber, etc.
Halo 4 and 5 introduced a lot that Halo fans were unhappy with. It looks like they’re all returning one way or another.
It appears the change in artstyle has fooled us into believing the gameplay was going to be fixed as well. What are your thoughts after viewing the Halo: Infinite demo? Does Infinite appear to be just another Halo 5? Or have we completely misread the situation? I’d love to hear some different opinions. 
EDIT: To be honest, I’m not convinced the artstyle has been fixed at all.
- The drop wall is not reminiscent of anything we’ve seen in Halo before. There are so many Halo shield designs 343i could have drawn from (the bubble shield, deployable cover, anti-vehicle barrier, shield walls, etc.) but didn’t. - The Pulse Carbine, which appears to be the primary Elite weapon, seems to be a burst version of the Storm Rifle. And no other weapon in the trailer looks remotely familiar besides the AR (which has never looked so untextured since CE). - The Brutes faces look flat and non-threatening, unlike the savage, angular, protruding faces of the merciless Halo 3 or classic Halo 2 Brutes. Even their armour looks far less distinct than anything we’ve had in Halo so far. - Taking the elevator up to the Banished platform with that “Commando” gun seemed like something straight out of Planetside, which is a great game, but it’s definitely not Halo.It seems 343i have very much mislead us with the previous Halo Infinite trailers. We are not returning to a more Halo-esque Halo. We might even be straying further from it.
EDIT 2: ADS
Some people seem to be confused by this. Let me clear it up a bit.
- Halo - instant zoom on specific weapons, clear and simple design - Halo 2 - instant zoom on specific weapons, non-combat zoom on other weapons, clear and simple design - Halo 3 - instant zoom on specific weapons, non-combat zoom on other weapons, clear and simple design - Halo ODST - instant zoom on specific weapons, non-combat zoom on other weapons, clear and simple design - Halo Reach - instant zoom on specific weapons, non-combat zoom on other weapons, clear and simple design - Halo 4 - instant zoom on specific weapons, non-combat zoom on other weapons, new Halo 4 design - Halo 5 - plays out an animation every time you zoom, zooms in with every weapon, displays some weapons on-screen during zoom, new Halo 5 design - Halo Infinite - plays out an animation every time you zoom, fade-in-fade-out styleSo no, technically Halo 5 does not have “aim-down-sights” but it features an animation typical of ADS rather than the standard instant zoom of most Halo titles. I hope that clears things up.