Miles Morales, Ms. Marvel, Spider-Gwen, Champions, etc., are on merchandise and were made for the new era of young readers of Disney's Marvel branch.
The X-Office was given a push to market the X-Men like in the 90's and 2000's, and did dozens of books.
Why didn't they take advantage to make a new young mutant to market as a solo character that could be marketed with other Marvel characters and solo?
They ended up opting for taking a well established character to avoid the hard work and slapping an X logo. Kinda like what Diseny did when they bought Marvel and Star Wars.