Kind of hard to argue that she wasn't an essential part of the movie. It was just an especially bland and uninteresting part of it. She had some major screentime, and an impact on Jean.
It's not lazy to understand the mechanics involved in taking a character who pretty much HAS to have ties to Charles Xavier and understand that this would shift more screentime to Xavier and take it away from Jean.
I don't recall anyone ever saying that, but they pretty clearly didn't use Lilandra because they didn't want to completely underserve the character. She was conceived as a key element of a two part storyline, where she would have had more adequate devleopment/exploration. If you read between the lines a bit...Marvel is probably going to use Lilandra in its franchise, and sooner rather than later.
Why is this incorrect? If they'd included Wolverine, audiences likely would have wanted to see that familiar element. That would require additional screentime, as would Wolverine's mere existence in the story.
They did have fiery Jean.
They had it when she truly "let go" and embraced her power, much like the previous film.
His reasons are perfectly logical and based on structural screenwriting concerns.
But Cassandra Nova would have required more time to tell the story, to develop that angle, and that would give more screenttime to Charles.
There are very real constraints when it comes to making a single film. Something like the Hellfire Club or even Cassandra Nova was probably just a bit too complex for a single film.
If they were going to have a somewhat "faceless" villain, they made the right call, I think, in terms of how it fits into the Dark Phoenix storyline and the fate of Earth. It just wasn't executed well.
