THINGS THAT WORKED:
-Ludwig Göransson's incredible score. It's like synthwave with talking drums.
-The cold open. Holy shit it's so intense and is everything you hoped a Nolan movie would be.
THINGS THAT DIDN'T WORK. EVERYTHING ELSE:
-The generic villain who's evil. He's also Russian because, of course he is. His motivation and way of thinking is so convoluted and actually makes zero sense.
-The characters. I don't get what they're doing or why they're doing anything except for Elizabeth Debicki's character (honestly a better title for the movie would've been "Schrödinger's Kat". Imagine Inception where the main characters virtually have no backstory and the main guy is just some rando who I guess is literally named The Protagonist (not my words. The movie literally announces this more than once).
-Sound mix. It was probably way worse in theatres but even the digital release version is pretty iffy. Nolan's excuse is that the experience matters more than dialogue. He is wrong. Even with subtitles on, the movie still didn't make much sense. If anything, he intentionally uses loud sound effects and music to mask how bland the dialogue is.
-Time travel. Even after watching and reading all of JoJo's Bizarre Adventure, I still couldn't follow the time travel elements in the movie. King Crimson just works. Tenet just doesn't. There's literally a character who introduces the rules to us near the beginning who tells us to not think about it. There's also a scene where someone explains the Grandfather Paradox to the Protagonist (because he somehow hasn't heard of it before) in great detail and then finishes by telling us to also not think about it. This extends to the reversed footage -which, on paper sounds cool and was probably extremely hard to shoot. But it just looks underwhelming and kind of boring after a while.
-Editing/structure. Nolan films love crosscutting scenes to move things along. Dunkirk was really more than what I could endure and Tenet is even less comprehensible than Dunkirk.
-Pacing. For a 2 and a half hour movie, it moves way too fast and never really takes the time to breathe or to properly show you why anything matters or how anything works.
Tenet is the only Nolan movie I dislike. It's a generic action movie that feels like a relic of the 80s with a nonsensical time travelling gimmick and a bloated runtime.