You are talking this up so much it's never going to live up to what you expect it to be but I can tell you'll be completely satisfied regardless. I'd also be curious to know what you were saying with Halo 4 and 5 previews, the campaigns for both of those games were awful. If you don't think everything in Halo is scripted to some degree you are crazy, that stuff is all designed to happen it's not random lol games don't work that way. They all have scripted events that just kick in when certain things happen, it's not like they are just making up random fights for no reason, it's always scripted lol.
First off, that's crap. Halo 4 was AMAZING. Don't buy the bs about the game being bad lol. It also has the best story in the franchise in my eyes, and the best version of Master Chief. It also introduced some additions to the sandbox I actually enjoyed for the time that they were present. Halo 5 gave us squad commands, which I loved, I got to play with Blue Team, it had the best pure gameplay of the franchise, but just had a very disappointing story with not enough Master Chief and Blue Team, and right when the story was getting really good is when it ended.
And how can the game never live up to what I expect when I'm literally telling you that I've not only read a lot of previews, but I've also directly watched gameplay footage. Everything I was excited about this game for, everything I was hoping for has been significantly exceeded, the only thing left is to see just how good the ultimate story payoff is, and how much better the campaign levels and story encounters become through the rest of the game. This game has everything I've ever wanted out of a Halo game. It's far, far, far more story driven than any past Halo title. They are going the batman arkham route in making you feel more like the character. In the same way the arkham games made you feel more like batman based on the gameplay opportunities and game design, Halo Infinite does just that with master chief in this game. Every single upgrade you acquire in this game isn't just some random, disconnected event outside of the game's story. Every new main upgradeable armor equipment you get is an actual legit part of the game's main story. That exceeds the level of story interconnectedness that I was hoping for. The way they tell the story in the environments and during gameplay are at a level that I've never seen before in Halo. Remember that Cortana vision Chief had in Halo 5 when he first told Blue Team where they had to go, and it was Meridian? There is even BETTER storytelling than that during live gameplay and with sick use of effects and storytelling elements that NEVER appear in a Halo campaign during gameplay. These are things that have been exclusively reserved for cutscenes only, but we are now getting some of the best bits during live gameplay. It's a massive overhaul of the way stories are told in a Halo game, and I couldn't be any happier about that.
Sections that were QTE in a game like in Halo 4, Halo Infinite right out of the gate gives you a set piece topping the entirety of the Halo 4 intro level plus cutscenes, but you do that shit in real gameplay, and you have a multitude of options on how to proceed and complete it. There is no "this is the only path or you fail" feel about it. The Halo Infinite opening set piece destroys the end of Halo 3's warthog run. That's how much this game is exceeding my expectations. The second Halo Infinite level I saw looks infinitely more jaw dropping and impressive in its storytelling effectiveness than anything in any prior Halo game. It's not even close.
So, yes, Halo Infinite isn't living up what I expected, it's far exceeding them.
What's another way it's exceeding them? Just go have a look at the capabilities of some of these bosses, and how these fucking elites are moving like something out of a ninja gaiden game, the way they jump at you, their incredible speed, and the amazing way that they slip in and out of camo. There's never been anything like it in a Halo game, such unique higher level boss behaviors. And some of these fights are fucking optional... if the optional enemies you don't even have to go after are playing this way, what does this campaign have in store for us? The strongholds gameplay, going after the big bases? They're actually living up to all 343 claims about you'll have many different ways to approach the situation. There is an almost insane number of ways that you can complete these objectives. The interplay between Chief and "The Weapon" or the new Cortana is another thing that has been far better than I could have hoped for, so trust me you don't need to doubt as to whether this game will live up to my expectations. It has already exceeded them for such a massive fan of Halo lore as myself. This is Halo at its very fucking best.
And don't even get me started on how awesome and open the levels are. The best parts of Halo 5 were the increased verticality of levels, but this takes it to a whole other more absurd level. So even Halo 5 not being perfect it had its good points, some of which thankfully make an appearance back in Halo Infinite.
Halo's gameplay is more dynamic and a lot less scripted than many other shooters like Call of Duty and a lot of others. This shouldn't even be up for discussion. Halo's enemies have more complex AI behaviors, with various traits and uniqueness about them that just plain makes them more fun to fight than enemies in more scripted shooters. Of course Halo has scripting, it just doesn't ever feel as scripted as in other games because Halo's battles can all play out entirely different from when you played them that day, the day prior etc. You do something different, the sandbox responds to you differently.