And nothing even happened in 2017 that felt like it couldn't have happened in 1984. Like did they absolutely needed to be in the future for the T-3000? He could have just as easily been sent to 1984. Also, why do they have to stop Skynet
a day before it goes online? Like they skipped 33 years where they could've stopped Skynet in literally any stage of it's development, but they skip all that and jump to the end where Skynet is fully developed and is actually able to speed up the process when it learns that it's under attack

. Only reason I can think of is that maybe the filmmakers thought that the whole 'Skynet is an app/OS' thing was a clever enough idea that it just had to be in the movie. I mean that's the only thing that wouldn't have worked in 1984.