I was figuring it was more like this being completely out of left field, because despite the quality of all the other T movies, they were centered around John Connor and leading towards the Future War we see in T1 n T2, if they had continued from Salvation since it took place in 2018(which a lot of people seem to forget, so I can't really buy their complaints on not seeing it.)
This suddenly happening with a whole new future and leader it's like...it's a complete left turn. So it's throwing everything for a loop.
Pluus....if John is dead in the past, then how does the Terminator that kill him even exist, or how does Sarah Connor even exist the way she does now? Killing John then, means...no Kyle Reese is sent back, thus no events of T1 and then no events of T2. So there would be no Sarah as a hardened trained woman ready to fight machines. There wouldn't even be an original future pre-T1 as well, because John wouldn't have been in a work camp and bust everyone out, so that future Skynet would win, they wouldn't have invented time travel to start with.
The only way it would make sense, is that....both futures exist, but the past is the same as both of the different futures. But even that doesn't really add up, unless the past is something weird in the universe where it's the same and yet could also change.
Also yes, I realize the multiverse thing for the Tverse was very much a thing in the lore material and Genysis, but the average audience moviegoer won't buy into that stuff.