I'm going to preface this with saying I like the game. It's fun and at its core it does feel like Thief. With that said...
This is the worst Thief game in the series. Which isn't a terrible thing; I just feel they missed the mark for what makes a great Thief game. At every turn I get the sense that the management behind this title aren't die hard fans of the series or they completely ignored what made the games so compelling. Not that Thief was ever some holy grail of game design (it's up there) but there were several core tenants* that they completely ignored or reduced in favor of making it appeal to a much broader crowd. It's also pretty shocking just how limited and small a lot of the levels are for a game that I assumed was built for PC and next-gen consoles in mind. They do a lot of clever gimmicks to hide room loads (opening a window or passing through a narrow passageway) but the levels still feel rather small since you're always booking from one cramped gameplay encounter to another. It's not that this new Thief omits any core stealth gameplay mechanics; it just doesn't do it as well as the previous games.
Dishonored is a much better game. Arkane Studios understood stealth and executed really well which isn’t surprising considering Harvey Smith was at the helm. Dishonored literally does everything better than Thief and I actually didn't really appreciate just how much Arkane nailed it until I got my hands on Thief. I still like Thief, but man does playing it really brings to light just how vast the gulf between utilitarian and great game design is. Even simple design concepts like gently illuminating the path towards the next player objective or providing ample player experimentation with newfound abilities is nowhere to be found. Instead we have an over-reliance on HUD markers and your usual next-gen lazy bullshit design methodologies** to make up for subtle player direction. Even the art direction is superior in Dishonored and I'm finding myself preferring the visuals of that game to the new Thief, even with it's sharp 1080p resolution and pretty nice environment effects. I could also talk about the awesome powers you have in Dishonored but I get that Thief preferred to keep their powers centered on improving established mechanics instead of new ones. However Dishonored's Blink was a really smart improvement to the stealth genre, I thought.
Thief actually does get a lot right. One of the things I find really enjoying is the sense of physicality Garret's character exhibits when moving around. I dare say this is the best "feeling" first person game out there with every directional change, dash, and movement having a sense of real weight. Even complex actions like getting behind a corner and peering around (handled rather daftly in Deadly Shadows by switching to third person) is effortless and even fun in the new Thief. I also like the changes to make Garret feel far more acrobatic and capable making environment navigation and combat no longer a chore. Although stealth was and still is king, it's nice to finally play a Thief game where I can play the character as well as his background indicates. Other nice changes are the upgrades the player has at their disposal to improve Garret's "Focus" abilities. Implementation is super game-y but it's nice to customize my actions to my specific play style. That customization even extends to the difficulty where you can turn on or off as many gameplay rule sets as you'd like so you can play the game a-la Thief classic or go full on with the new changes. There are more examples but those are the biggest off the top of my head.
Well typing all that out felt a bit cathartic considering how long I waited for a proper Thief sequel.
spoiler (click to show/hide)
* Multiple player paths, intriguing background story, fantastic NPC script, finely tuned balance between player empowerment and vulnerability, expansive level design, etc.
** Various in-game cues to indicate action, on-screen text explaining simple controller commands, overdrawn tutorials teaching basic gameplay concepts, limiting player action and abilities until they are properly taught, overtly linear level design, forced cinematic encounters spoon feeding story, player overwhelmed with gameplay options with minimal strategic difference, etc.