One thing about Crucible is isn't just about getting personal power back, but a sense of legitimacy in mutant society. The mutants organizing Crucible are sending the message that if you don't have powers, you aren't a fully worthy member of the culture. Xavier says "Krakoa is for all mutants". But Crucible says "you don't get Krakoa, not really, unless you sacrifice yourself." Crucible is means testing for what all mutants are supposed to be given freely.
As part of that, it is also spreading the notion that if you aren't willing to die for mutants/Krakoa, you don't deserve respect. It's kinda more dangerous that Crucible isn't about power levels. It is not for brave mutant warriors to prove they're willing to fight for mutants. It's seeing who will volunteer to get slaughtered even if they're not built to be a warrior or fighter.
This is the exact opposite of what Crucible is. Go back to Xmen #7. Kurt explains why he's uncomfortable with the concept (because it involves death and violence, basically) but ALSO concedes that Crucible exists because council was faced with a problem.
What happens if one million depowered mutants decided to all kill themselves tomorrow (via taking a bunch of pills, falling asleep in the garage with the car running, or straight up eating a bullet) in order to get their powers back?
It would present a tremendous problem for The Five in drastically expanding the already-really-freaking-long resurrection queue, and Council doesn't want a mass epidemic of mutant suicide.
This is echoed in the words of Apocalypse the same issue.
"look around you. Look closely. These are people willing to fight to the very last one to preserve our way of life. And this is why we *do not accept* those like you simply killing themselves to be reborn as something better. Its surrender. And those days are behind our people. Do you understand? "
Crucible exists because council anticipated a large number of ex-mutants embracing suicide as a way out- which they considered unacceptable for various reasons- and got in front of it. You kill yourself? You're not getting resurrected for a VERY long time, if ever.
Resurrection and restoration is available, but only to those with the will to fight and die for that right.
Consider again the words of Apocalypse in Xmen #7-
"You CAN live like this. Like a human. Its an existence of a sort. There is nothing wrong with it."
The depowered are free to live in paradise as they wish to the end of their natural lives on Krakoa or the Moon or Mars or Shi'ar space or whatever without penalty. They aren't second class citizens.
"We can make the pain stop. Your wounds will be healed. We have mutants that can make you whole. All you have to do is quit."
There is always a way out during crucible. If the pain is too much, the fear of death is too much, if they simply aren't a fighter- the option to stop is always there, without judgment.
" Accept this gift, you have earned it. "
Death in crucible and thus rebirth at the front of the queue is a gift that is earned by those willing to fight and die for the privilege, and by extension willing to fight and die for Krakoa. The line of mutants killed unfairly on Genosha is millions long. It is just and fair that expedient resurrection ahead of those people would be reserved for those who show determination.
And "determination" and "fighting skill" are not the same thing- "Lost" clearly was not a combatant, nor able to put up any sort of defense to Magneto when she faced him. She can barely string a sentence together.
Its not about who will "volunteer to be slaughtered" its about those for whom living as a mutant is a value above all else.