We're talking about condensing two different storylines (Phoenix Saga and Dark Phoenix Saga) into one movie, and I'm not convinced it's that easy.
Yes, a lot of Dark Phoenix Saga is set on Earth, but Phoenix
is established as an intergalactic threat because she eats a solar system, so a Galactic Council decides she has to be put down. And let's not forget that the "aliens" are introduced on a previous issue when the X-Men are caught up in a space dispute (they travel to an alien planet) over a doomsday crystal, where the Good Phoenix saves the day. It's very serialized and not a self-contained story like the two issues of DOFP -- you could almost make a trilogy out of it but I'd settle for two films. The issue is not the drama but the downplaying of the intergalactic elements of the story.
It's possible Kinberg took notes of that WatX version. But even that version had the Hellfire Club
. Maybe Chastain is Kinberg's version of Eric the Red, except with an entirely different purpose (to manipulate Jean instead of killing Xavier). Genosha doubling for Cassidy Keep/Muir Island? Anymore comparisons seem to be pushing it.