It was surprisingly watchable for being as shytty as it was. Outside of the dragging opening sequence the flow was smooth enough to kinda make up for the moments where the movie would go off the deep end as they'd try to explain or make sense of the time travel like it isn't a giant clusterfukk. I cringed every time they kept throwing these random science terms around like 'quantum field' and 'nexus point' and pretend that somewhere it was all supposed to make sense.
They had a couple good ideas too, like the concept of the John Connor Terminator was kinda cool (like him 'morph/shock waving' through Arnie) but they didn't show off his abilities nearly enough so until the fight scene against Arnie you could replace him with a T1000 and it wouldn't change a damn thing.
I can say I was surprised with Emilia Clarke. While her best wasn't always good enough, I at least felt like she tried and gave it her best shot. Her face and physique are just too innocent looking to pull of the hardened fighter chick though (she can't help it that she's like 5'3" but working on her physicality would've gone a long way). Arnie did his thing although I felt some of his early line delivery was really bad, like he was forcing the accent way too much. I noticed it less as it went on but that might also just be because his lines got a bit better.
Jai Courtney... geez. A wet towel has more charisma than this dude, let alone the utter lack of intensity that is necessary for the character. The worst is that like Clarke I felt he was really trying too, which makes it all the more sad.
The action was just kinda there, enough to keep you watching but not interesting enough to make you remember. Like I said, they should've put way more effort into showing off the new Terminator abilities and create new dynamic fights that way instead of rehashing the same old same old with him as a T1000 placeholder.
Oh yeah, that shyt at the ending with Genisys was hilariously bad. The concept of an avatar of a computer program aging, and this somehow speeding up the process it could upload itself because the computer program growing up means it also becomes better at doing what it does, made zero sense. That shyt literally made less sense than the time travel shyt. And the way they kept shooting the holo-cameras to shut him up for like five minutes too while dropping a "why don't you just shut up!" line every single time, fukk, that shyt was bad. Add Arnie randomly upgrading to a T1000 model (made absolutely no sense either, not even with the poor attempt to make sense of it with Byung-hun Lee's T1000 being able to reactivate the T101 model early on in the movie) and the entire climax of the movie was just Blade Trinity levels bad.
I didn't hate it too much because like I said, it's surprisingly watchable despite a lot of things being wrong with it. For the life of me I wouldn't recommend it because there are far better ways to kill two hours of time, but there are far worse ways too. Like rewatching Terminator Salvation for instance.