Carol became a solo character recently with the Ms marvel book, Rhodey is more of a supporting role that get some minis.
Wonder Woman and Aquaman both have been having solos for like 75 years, so they developed their core casts. There is no wy to compae them with Rhodey and Carol.
Rhodey being a iron man character doesn't make him another franchise, he can still guest star on both Captain marvel and iron man books.