Every negative review is literally written by someone who:
A. didn't pay attention until the last 20 minutes
B. paid attention (doubtful) but couldn't comprehend.
C. they hate M Night Shyamalan and it's painfully obvious (I didn't even know it was a Shyamalan movie until I went to write this review)
It's fine to not comprehend on the first watch, but that's not automatically the fault of the film. At that rate we might as well just be producing kids movies for adults if you just want to stare blankly at the screen and come out feeling fuzzy inside without any additional thought required on your part. Please, please, please ignore the reviews telling you not to waste your time. Watch the movie and decide for yourself, but I promise it's not a "waste of time". It's 1h 44m, there are far longer and far worse movies to truly waste your time watching, this is not one. If you come out of this movie "dazed and confused" the takeaway is not that the movie sucked, it's that complex stories/timelines are not for you, to put it nicely. Leave them for the adults (and inquisitive kids)! And if you didn't like this movie, don't even bother with Tenet, go draw with chalk on the sidewalk or something instead.
I'm not saying this is the greatest movie of all time, but it's at least worth a watch.