If at first you don't succeed, you'll need to shoot everyone all over again
In a way, Deathloop feels like a retort to my FOMO on Prey's story choices: if you "miss" something, you can try it again tomorrow! It's a great wrapper around Arkane's dense and intricate levels, even though some flawed progression and poor storytelling keep it from reaching "masterpiece" status.
The game unfortunately puts its worst foot forward, its intro forcing you through a linear series of narrative-setup and tutorial sequences; you can't choose your own objectives or destinations, you can't even use "Residuum" to save equipment for the next loop. And while the sci-fi mystery plot itself is intriguing, main characters Colt and Julianna distract from that plot with their aggressively one-dimensional personalities.
"Angry" and "violent" are character traits. Not full characters. Colt and Julianna deliver some fun one-liners, but their dialogue lacks any of the curiosity or introspection that'd help players connect to their crazy situations.
... anyway, once it's done with the tutorials and unlocks your Residuum, Deathloop opens up to reveal its real strength: self-directed investigation. Colt's objectives of finding the Visionary targets, figuring out how to manipulate their schedules, and snatching their Dishonored-like magic powers ("blink" is called "shift," now) make for a deeply-satisfying time-detective adventure like Majora's Mask or The Sexy Brutale.
Deathloop is at its best when it combines this murder map mechanic with the sneaking, shooting, and trap-exploiting principles of Arkane's previous games. Now, finally, when you see a locked safe or an unpowered gadget on your way to something else -- the game will remember that "discovery" for you, to make it easy for you to revisit in another loop!
So that's the good news. Here's the bad news: character progression kinda sucks. And not for the reasons you might think.
That is, you might assume that it's hard to collect enough Residuum to persist upgrades (it isn't), or that it's easy to die unexpectedly and lose everything (it ... usually isn't). The game is actually quite generous with the "Reprise" ability to respawn and recover your body, bar a few intensely-frustrating exceptions ("nullifiers" and a couple of body-snatching death-traps).
No, what limits you in growing Colt's power are a very small loadout and random item drops. You'll find and accumulate dozens of Character Trinkets, but can only equip four; piles of pistols, shotguns, SMGs and sniper rifles, but can only carry three guns; even the five "Slab" magic abilities are hamstrung by a loadout limit of two. And except for the Slabs and a handful of unique weapons, none of the upgrade pickups are scripted -- you're likely to see a lot of duplicate, garbage drops.
Since you can't change your loadout mid-level (except by picking up new guns), these limits discourage experimenting with situational or risky options. And you can't exactly go looking for a specific Trinket upgrade, since again, the drops are random and often garbage.
I really hope the next game gives you more real-time inventory flexibility, and uses scripted sidequests to reward you with high-value upgrades, instead of asking you to pull the lever on a random-drop slot machine over and over.
And I do want a "next game," another Arkane take on time-loop mystery solving, because adding that element to their intensely-immersive world-building is an absolute win. It's just a shame that Deathloop has so little room for upgrading yourself to fully conquer that world.
Better than: Dishonored 2, Dishonored: Death of the Outsider, The Sexy Brutale, Stories: The Path of Destinies
Not as good as: Prey (2017)
Probably better than: Dishonored, although Deathloop's sneaky and killy features are less robust, the ability to re-explore levels makes up for it.
Progress: killed everyone