We already have Sephiroth in this game! He just had a few more arms. And a few less letters.

In honesty, I do think Zenos is a play on the general archetype that Sephiroth is a part of, the 'pretty human (or human-seeming) side-antagonist that starts off appearing relatively grounded and equal but becomes a much bigger threat through magical means'. (See also: Seymour, Vayne, Kuja.) It's a formula that works, so why not use it? And similarly, knowing that there's some visual elements of Sephiroth scenes that work... why not borrow them, too?

Of course, they miscalculated and forgot to copy any of the reasons Sephiroth is interesting, so ultmately it's less of a true recapture and more of a hollow resemblance with similar plot beats.