Okay, yes, it was largely garbage. But I watched the first third of the movie last night for what I believe was the third time, and maybe it's growing on me. I'll grant you, I wish they hadn't used nanites at all in the movie. And the whole dip-Arnold-in-magic-metal bit at the end was absolutely ridiculous. But the film did have a few things going for it.
First off, the re-creation of Arnold's first 1984 appearance as The Terminator was well-done. The replacement actors could never have matched the late great Bill Paxton's punk, and I personally very much missed the original alleyway hobo from Terminator 1, but having old Arnold pop up to confront young Arnold was very cool, and the crazy unexpected turns the film takes from there rival the surprises we saw in early moments of T2. I've often said (especially of Terminator 3) that the films don't all need Arnold. But if you did want to get him into the film, this is a pretty good reason.
Next off, I've got to say that they consistently find great actresses to play Sarah Connor. The best remains Linda Hamilton, in no small part due to the incredible transformation she underwent between the first and second film. But Lena Headey also did a great job with the character in the short-lived television series. And Emilia Clarke's Sarah Connor in this film was also really really excellent.
Consider the opening of Terminator: Genisys. They swap things out. Kyle Reese, the savior, is suddenly the one who's clueless as to what's going on, and he's being saved by Sarah whom he'd expected to be a soft and clueless waitress. She and "pops" take out the original T-800 and shortly thereafter take out a liquid metal T-2000. In a quick one-two punch, they defeat the unkillable nemeses from the first two films in the first act of this one. This is the part I watched last night, and I know that the film as a whole was trash, but I did really enjoy the opening.