Movieman630’s review published on Letterboxd:
When reviewing films I tend to forgive flaws if they are a result of risks being taken. As such, Tenet is the exact kind of film that I will review more kindly than others. The plot is very difficult (though not impossible) to follow, but that is due to the driving force of the film being a cool new idea. As a narrative, the plot is a bit too complicated and exposition driven for its own good, but as an exploration of a concept it's very solid.
As far as character work goes... this isn't really a film that's interested in that. Both John David Washington and Robert Pattinson's characters are sort of blank slates. Thankfully, Elizabeth Debicki and Kenneth Branagh's characters are far more fleshed out to the degree that one wonders why they weren't the main focus of the film.
Overall, the biggest knock against the film is probably the sound mixing. The plot is complicated enough, but it's often very hard to understand what the characters are saying. The editing is often great, mixing the conflicting timelines in interesting ways, though there are a few moments where it becomes difficult to understand what's happening.
As far as high concept original sci fi action films go, this is a great example, if not quite as strong as Inception was. It's perhaps not truly a great film, but it's incredibly engrossing and will leave you thinking about it long after it's over.