Okay, I know we all dump on Dark Phoenix for ignoring the Dadneto storyline, but can we talk about Apocalypse for a second??
En Sabah Nur had the whole ‘father of mutantkind’ thing going. Meanwhile, Peter wanted to find Erik, his dad, but obviously wasn’t sure how to feel about him. You could see it in his face when he watched the news report, his reaction to his mother’s warning about Erik… he even asked Raven if Erik was a bad guy.
Erik losing his family and becoming the bad guy again… it minimized the impact him joining Apocalypse, because it was so obvious. But… if Peter loses his mom and sister, then you have a parallel which deepens the dadneto storyline
A powerful speedster (with dormant metallokinesis) is exactly the kind of mutant Apocalypse wants as a Horseman. A father-figure who promises vengeance and justice against the humans is what Peter thinks he needs.
Peter doesn’t even have to fully believe in En Sabah Nur’s goals. He’s alone in the world, drowning in grief. More than that, En Sabah Nur gave Peter more power and a purpose. He tells his Horsemen that they matter. The world may have cast them aside, but Apocalypse chose them.
On the other hand, you have Erik. He goes with the X-Men to stop Apocalypse. He’s there to rescue Charles, but he also owes Peter a debt for breaking him out of the Pentagon. He and Charles found out what happened to Peter’s family, Erik knows what it’s like to watch your mother die while you’re powerless to stop it. Regardless of whether or not Erik knows before Cairo that Peter’s his son, he knows the pain the dark path of grief-fueled vengeance brings, and doesn’t want that for Peter.
Erik finally comes face-to-face with Peter, by that point aware of their relation, and promises him that Peter’s not alone and will never be alone again.
You can even still have a Sweet Dreams scene with Peter using his powers to save the X-Men and/or the remaining civilians in Cairo, followed by him fighting Apocalypse.
When his leg gets trapped in the ground, and Apocalypse angrily demands, “You betray me?” there’s another opportunity for a visual parallel between Erik and Peter. With En Sabah Nur focused on him, Peter uses his metallokinesis to stab rebar through Apocalypse’s chest (like Erik using his power to get the helmet off of Shaw in First Class.)
None of this is far-fetched in the slightest for these characters, and develops the Dadneto storyline in a much deeper and meaningful way. It’s not as predictable, because it doesn’t force Magneto to be the villain. You have the dichotomy of En Sabah Nur’s ‘father-figure’ approach (it requires sacrifice on Peter’s part for En Sabah Nur’s benefit) and Erik’s paternal approach (he puts himself in danger to help Peter).
Anyways, a huge missed opportunity, and now I’m sad, so…