The ST was never planned out just by the mere fact they never knew who Rey was going to be as confirmed by Daisy.
Exactly. Whether you hate zack snyder or not that guy had a plan for his movies starting from bvs all the way thru his 4 hour justice league epic (which was originally supposed to be 2 movies). So he basically mapped out a whole trilogy worth of story material prior to compeleting bvs with threads that connect all the way through the movies. Warner ****ed up that plan which was why justic league was so bad, you can sort of compare it too disney knee jerk reaction to tlj. In either case if they had plan at some point to connect all the story threads they failed miserably doing it. A good plan would have mapped out reys arc from the start in a logical way or even planted the seeds for the real villain in tfa, if it wasnt supposed to be snoke to begin with
Take man of steel and bvs the zod battle mirrors each other in mind blowing perfect detail just from different perspectives. Disney couldnt even link the end of tfa with the beginning of tlj without it feeling jarring- luke all serious to luke being a dumb **** tossing the saber over his shoulder