Mutants were old? Not per se, but it did take a new batch to offset long time established characters. A bit of new coming and going attractions with a bit of promise to return! Established even in overseas distribution, which in and of itself is a modern feat brought to us by the late 20th Century! Those scurry mutants were found all over the world, all while Marvel was in the think tank discovering what was good! Xaiver known all around town, as word of mouth travels fast...
That recuperates faster than a healing factor to know therein lies the rub of the mutants who are new and making head waves in 1983!
Mutants are uprising, well kind of, they are at least new, and specifically to the Copper Age. The off-brand team was and were new to their style of writing and art, it first to feature Rob Liefeld in a steady work or one of his first characters. Those Legion and Cable like stories were ending and yet still a newer beginning by the time as Deadpool came and was a administrative success, eventually. Those are the breaks when newbie rolls the dice! It took some alterations to all of the above for something to hang your hat on to cling too. Those stories were all very modern but motivated as well especially the artist for #24 and Legion. His name is Bill. Kind of like the edge had lost its keen, it was then renewed with luster upon the newsstands of New Mutants. "Ooh! What is that?" It could be heard and the reads had enough text with substance as well, more than one or two a book as well!