Well Claremont is not exactly source material.
1. the original 5 were not written by Claremont
2.Grant Morrison had a good run.
3.Whedon had a GREAT run
4.Hickman had fantastic run as well.
No, but the book didn't sell and what we think of as "the X-Men" didn't happen until Claremont re-cast it with his all-new, all-different international lineup. He wrote the book for about 20 years. As soon as he stopped writing, I stopped collecting. Now, I know the kids will like their era, and that's fine, but I'm just saying for me... Claremont IS the X-Men.
Given that the movies have used primarily his vision of the characters, in his universe, and his stories... Hollywood largely agrees. Claremont made the X-Men what they are. They are not the iconic figures they are if he doesn't take over the book, they would be on the same level as the Guardians of the Galaxy or the Defenders.