I would say the responsibility is on the writer to tell the story he wants to tell...which may or may not entail what we the readers think should be written.
In this instance...Yes, we believe there should/could be better interactions/support between the various MU Superhero teams and Mutants...and some writers may believe that too (as evidenced by the pages ElectroM posted.
But...they are not beholden to show or write that if it doesn't serve their intended story.
As these things go, given the circumstances, support has waxed and waned over the decades...it's really not that big of a deal.