The changes are nonsense yes. I also went back and compared the OG's narrative at this point and Sephiroph was way more coherent in why black material was important and actually explains that when the earth is done massive damage, it will draw in immense amounts of energy which he will take advantage of. In Rebirth he waffles on for ages and it's unsatisfyingly cryptic.
I honestly haven't processed much about the branching timelines so I can't respond specifically to your sentiment, I just think they made the story worse and more convoluted.







