I had higher hopes for this. Story by James Cameron! The return of Linda Hamilton and Arnie! But, eh.
Those old tricky time-travel paradoxes are in force here. We are invited to ignore the last three Terminator movies, apparently because they sucked at the box office. In this timeline, John Connor doesn't make it through the opening scene, because yet another T-800 (Schwarzenegger model) blows him away in front of his mother, Sarah.
There's some mumbling about how the timelines work, but the bottom line is that the preferred method of evil-AI warfare is still to send advanced Terminators back in time to prevent the future leaders of the AI resistance from existing. And, what are you gonna do, the resistance sends back an intrepid soldier to prevent that. What ensues is a lot of CGI-assisted mayhem. Much of it (I won't lie) is impressive.
And there are some funny lines. But this one sucked at the box office too, so maybe we can Move On. (Or maybe there will be a movie about how James Cameron went back in time to write a better movie. That one, I'd watch.)