The high-concept idea of Tenet is perfectly fine. What if the flow of time was reversed for antimatter? Great! Probably a better idea than the one Inception was based on, to be honest.
The actual exploration of this concept leaves a lot to be desired. When a machine which can invert the flow of time for an object (or person) is found... it's just not a big deal for the characters in the scene. It's just there.
The characters . Seemingly important characters come and go and it's almost impossible to figure out who they are or what they do. This is by far the starkest difference between Tenet and Inception: Inception actually had characters.
The, ah... let's call it a twist, in Branagh's character is . Right up until the last few scenes, there isn't really any reason to. Andrei is made out to be an incredibly wealthy self-made (to the extent one could be) Russian oligarch, having made his money from.
There's just not really any reason for this. It's entirely plausible — and arguably
It's a generous eight stars out of ten from me.