It was a bit gimmicky but the magic square was used sorta :
SATOR is the name of the antagonist
AREPO is the name of the unseen forger
TENET is the "fight the future" organisation
OPERA is where the opening operation took place
ROTAS is the free port company
That being said I feel it's a meh movie with good ideas. The problem is that I am not sure it's possible to make a good movie with these good ideas. The script manages to convey the overarching stakes of the plot, but things are not clear enough to make the plot work on a scene by scene basis. The delay we have as an audience to try and make sense of what is happening also totally dulls the impact of any kind of plot twist or revelation. Maybe there were ways to make things work, like having it character driven (here we have empty shells and caricatures) or making it unintelligible to the point of abstraction (a bit too artsy for such project though, Nolan has a lot of freedom but not to the point of turning a blockbuster into Last Year at Marienbad), but we'll never know for sure.
I see some people have been very impressed with the car scene and the finale, but I must say I am less convinced. It feels to me the inversion concept did not translate into action scenes as creative and impressive as one might have hoped. I mean the car scene does not hold a candle to Matrix Reloaded or even some of the Fast & Furious ! And the finale battle is advertised in the briefing as "having everything", but it's mostly a whole lot of nothing except for the building caught in the temporal crossfire.
Still, it's a mostly enjoyable watch, thanks to a nice pace, an intriguing - even if flawed - original plot, some nice lines and, as always, Elizabeth Debiki.