I mostly agreed, but I also think nobody really tried to give these characters their own hooks as solo stars away from the X-men.
All attempts I can recall were ham-fisted. I remember how disappointed I was at Storm's last solo.
The popular Avengers don't have that problem because they were always solo stars first and foremost. Even other teams like F4 suffer from a similar problem as only The Thing had a lenghty solo run in the last decades.
For the X-men the problem is also bigger because the fact that they are not generic super-heroes and are deeply tied to mutant matters can actually limit the scope of what readers expect from them.
I do think Storm should care about more than just mutants. They could explore her fighting against other types of injustices or even have her take it upon herself to protect the world from threats against nature.
That teen Cyclops solo was actually fun for a while because it was actually about a father and son's relationship developing in outer space. That's a different concept. It didn't work for an ongoing, but I'm sure writers could come up with interesting directions.
And then there are characters like Magik, who actually do have a whole rich mythology around them that isn't necessarily tied to mutants but never got the chance to prove themselves as solo stars.