The more I think about it, the harder it is to choose.
As I have said elsewhere, X-writers have chosen Tribalism, full stop. But because it is the other side of tribalism, it's harder to recognize and thus speak up against.
When most think of tribalism, and the treatment of 'The Other', we need of dehumanization.
"You're Japanese? Eww! You must like tentacle porn!"
But there's another end of the spectrum, one rarely seen. Wherein 'The Other' is elevated, because they are other. That they are better, more righteous because they are not us.
"You're from Tibet? You must be so spiritual!"
For example to exploit this, and to dodge racism, in the 1960s, some African American performers pretended to be of any other nationality, like Korla Pandit (https://en.wikipedia.org/wiki/Korla_Pandit). I'm hard pressed to blame them, but as they are fictional characters, the X-writers have no excuse for the same.
Mutants are now that 'Other'. They are elevated and revered by their writers for not being human and thus, not having not having the flaws therein. Hell, they can somehow mass produce a metal that the freakin' galaxy can use as currency, without any industrial base at all.
And any who oppose? Any humans are just jealous and nothing more, or worship them likewise.
Mutants are no longer human in that they share any meaningful flaws. Hell, even the kindest among them (Nightcrawler), can kill without batting an eye.
And the kindest, most empathetic human, Moira? Only technically mutant, but since she was always 'human coded' and thus, the cruelest of them all.
So, to bring this back to the original point, which human do I miss the most?
All of them.
Because when we had humans, mutants were relevant to the world as it is, and a literary criticism of our world through metaphor. When they are an elevated other, they are little more than a mouth piece for complaints.
And we have more than enough of that.