Hamaguchi talks about the difference between FF7 OG Sephiroth and Remake's Sephiroth in a Q&A session in Square Enix Shanghai. Here's the question the interviewer asked as well as Hamaguchi's answer, summarized as it's quite long.
Question: In the FF7 OG, Sephiroth and Cloud seem like arch rivals. However, in the Remake series, it seems more toned down. Why is that?
Hamaguchi: Cloud and Sephiroth were actually never really portrayed as rivals in FF7 OG. Kitase often says this, but Sephiroth was a fearsome character in FF7 OG that you can't really see, but you can feel his intimidating presence, kind of like the movie Jaws.
However, the Sephiroth in Remake is different as Sephiroth has a lot more appearances in the game, and he feels more real.
Since it's been some 20-30 years already, people already know who Sephiroth is. However, in order to make it more dramatic, in Remake, we want to bring out more about his character. For example, what are his true intentions?
So in Remake you can easily see how Sephiroth truly views Cloud.