Like I get not wanting to sacrifice his creative stories for the sake of someone else, especially when that person had their time with the character and this is Slott's time to make a mark. But what Slott wrote was bad and was almost certainly not as good as whatever Hickman planned. Like I get it, but at the same time... No. Plus it's not like they couldn't coordinate or compromise; XM/FF had like no impact on Slott's run, and Franklin could jump between New York and Krakoa whenever he wanted. We even saw a bit of this in Slott's FF.
Aside from terraforming Mars? A lot of them got use. Exodus got a big glow-up in Immortal X-Men. Jamie was King of Otherworld for a hot minute. Iceman didn't live to his full potential, but he got a one-shot, that Unlimited arc, and a mini to himself. Gabriel wasn't super deadly or anything, but he was a notable recurring antagonist in X-Men Red. Legion co-starred in 2 of the 3 Nightcrawler books. Jean, Ororo, Magneto, Hope, Quire, all pretty obvious. Even most of the Arakki got love. When Omegas appeared, they often got focus or showed off how powerful they were.Also, is worth noting that Krakoa had a lot of teases that promised to be great storylines and end up as nothing. Remember that Omega list? How important was it in the end?
A lot of ideas fell through the cracks with Krakoa. But Hickman established the connection in as late as Timeless, is more than capable as a Franklin writer, and we got a mini specifically to establish plot lines between the Fantastic Four and Krakoa. This was clearly wasn't something they were just tossing around.
Franklin burning through his powers is sadly a constant running theme with him, so he'd have the biggest excuse not to help. He was already burning through his powers during the Krakoa era. And I don't know where the current Fantastic Four run fits in with the timeline, but Franklin was transported a year into the future around the time FoX started. So he wouldn't be able to help anyway.Fans are always asking why the Omegas didn't solved the Orchis problems, Franklin would be just one more not doing enough.