By the same logic, it bears repeating: Genosha may be important to Magneto's story, but Magneto is not important to Genosha's story. Which I see you do follow by the rest of your post, but then say Magneto, along with Rogue and Gambit, need to be there essentially cause they're household names.
Which in essense is saying that all characters besides the "household name" ones shouldn't exist and shouldn't be used, since anything meaningful they have to offer should just go to characters considered "household names." Or to put it another way, that characters that didn't benefit from the Claremont era should ever get anything in any adaptation of the franchise.
I do also see you mention how they're part of the main cast, but that's been thoroughly argued against by many people pointing out how the episode had plenty of other random mutants in it, and how easy it would've been to just have a quick few seconds for Lorna.
I think specific people who work at and with Marvel have something against Polaris. I gave receipts of that last year with White. It's not "just business," it's biases that these people have against certain characters leading them to make asinine changes. It would be like if I worked in one of these positions at Marvel, had everything Havok's ever done treated like he had zero involvement, and then claimed it's "just business."
This "business" talk is nothing more than excuses to justify biases and bad behavior. This is the exact same argument that executives have used countless times to prevent female characters in various media from getting their due. It's a false argument that WB execs used to insist Green Lantern deserved a live action film but not Wonder Woman, back in the early 2010s. It's the same argument Ubisoft execs made to insist Assassin's Creed games should mainly be male characters, why Eivor in Valhalla couldn't be just female, etc.
"It's just business" is nothing more than a cover for people in creative industries to justify doing things they know are wrong. That holds true for this right here.