Wonder Woman is just as great a solo character as Batman or Superman and she deserves a solo franchise just as much as them.
And I still love both of Patty's WW movies, but I'm very ready for a new WW.
Might be a hot take, but I'd argue NONE of the main JL are better in group stories. I feel like that's a cop out that people tend to jump to for the characters they simply don't care as much about. I might say it about The Flash, for example, my personal least-favorite League-r, but I know for a fact that both Barry and Wally have plenty of fans of their solo adventures. While some characters shine more in the group books than others, depending on their dynamics with the rest of the group, I'd still argue the group books almost never serve the characters better than their own stories, imo.