Halo Infinite is the best Halo campaign 343 Industries has released but, in my opinion, still doesn’t quite reach the bar set by Bungie's original trilogy. The story was decent but I probably would have been lost if I hadn’t just redone full playthroughs of Halo 1 through 5 of the month before release. Even then, I don’t feel like they did a great job setting up the Banished or why the Elites are willingly working for Brute leadership. The plot twist for The Weapon was predictable long before the twist was revealed, especially for players who know their Halo lore and/or collect audio logs along the way. I personally really disliked Echo-216 despite his plot arc, which made a major portion of the final act of the campaign feel less impactful overall.
The biggest problem with the story is it doesn't really go anywhere. It drops the player into the action six months after the intro cutscene and doesn't spare much time for exposition outside of audio logs until the final act of the game. The story exists almost solely to 'fix' the decisions they made with Cortana in Halo 4 and Halo 5 and, by the end, essentially serves as a soft reboot for the Master Chief. The two big bads in the game are just speed bumps along that path and other characters from Halo 4 and Halo 5 are given very short shrift.

I'm torn on how I feel about the open world nature of the game. It's very Ubisoft-y, which is to say it's loaded with collectibles and sidequests that are only tangentially linked to the main story. The Banished High Value Targets and Banished Outposts are prime examples. Completing these have no meaningful effect on the game world as a whole except to provide you with a boost to your Valor, a game 'rating' that unlocks special things at Forward Operating Bases. Once the player leaves Banished Outposts, the enemies respawn as though they never lost them. Enemies, but not the targets themselves, respawn where the HVT's once stood. One would think that dismantling the Banished leadership and infrastructure would at least lead to different dialog with the Banished leader in the late game, yet it does not. The open world just kind of exists, almost as if it's a separate afterthought from the main game. Infinite starts with two linear missions, then dumps the player out into a shallow open world sandbox, before ending with the final third act that's entirely linear and doesn't allow the player to return to the open world until the story is complete. In that respect, Infinite feels like it's trying to straddle two worlds: The crafted linear narratives of Halo games past and an open world design of the present.
Like other similar open world games, it becomes rote about half way in, especially because there's no real diversity in biomes. The world itself is just forests, mountains, and some protruding Forerunner structures; there's no snow, no beaches, no deserts. After a while, it begins to blur together. By the mission Pelican Down I found myself becoming bored with the constant repetition of capturing FOBs, defeating outposts, and collecting items. It's not as tedious as recent Ubisoft open worlds thanks to Chief's accelerated walking speed, the fun of navigating using the grappleshot, and the early access to vehicles. On the topic of collectibles, I was a bit disappointed in the armor unlocks found throughout the world as they are mostly color schemes, weapon and vehicle color schemes, nameplates and a handful of weapon charms.

Difficulty is inconsistent throughout. Rank-and-file enemies are easy, even on Legendary. But bosses, including the High Value Targets, have a major difficulty spike on Heroic and Legendary that is almost in the realm of Dark Souls. They are very punishing unless you learn their patterns and often have a host of cheap abilities that can easily kill you if you make one mistake. The final three bosses are extremely brutal as are some of the later area Banished HVTs. This isn't a dealbreaker but it can be very frustrating to go from an open world where Brutes, Elites, and Grunts are absolute morons to running into bosses that can sneeze from across the room and kill you.
The campaign is also riddled with bugs. Achievements that don't properly unlock, dumb enemy AI in vehicles that fly into trees and mountains, dumb friendly AI that get stuck on textures, checkpoints sometimes not registering (which can occasionally corrupt save files), multiplayer cosmetics not properly unlocking after opening armor lockers in campaign, frequent audio cutouts, and several instances of graphical stutter sometimes with graphical freezes lasting a full 5+ seconds, and this was on Series X where it happened in both Performance and Quality modes.

Halo Infinite should be called what it is: Retail Early Access. Taken as a whole, including both campaign and multiplayer -- because Halo has never in its history been campaign only -- this game is missing a lot of features that are/were considered staples of the Halo franchise. By 343's own statements, many of these things won't be around for months. At time of typing they've announced that they're adding Slayer variant playlists next week, which is a good first start but there's much more to do. By the summer, Infinite will resemble a complete game with campaign coop, forge, more maps & modes, dedicated playlists, campaign and multiplayer bug and server stability fixes, mission/level replay, et cetera -- all things that are lacking at launch. Releasing an incomplete product and patching in major things later is becoming far too common practice from 343. They did it with Halo: MCC, Halo 5, and now Halo Infinite.
In its current state I give it a solid 7 with the possibility to become an 8 or 9 over the next several months. However I can only review what is in front of us now, and it's missing too many things and has too many bugs, to score it any higher.