Jump just seems to be taking mangakas from Jump Plus and Giga and giving them opportunities instead of bringing back past mangakas that we loved. I find it interesting every time there’s a new round they’re almost always from one shots or mini series in Giga
GIGA seems to be the new place where they cultivate new talents and eventually bring them over to WSJ if they're ready. Mangaka can find success in Jump+, but it's still small compared to what you can do in WSJ. I think WSJ has a pretty good strategy right now.
If future attempts to bring over ideas from GIGA fail, they'll probably change their plan again.
A lot of older mangaka probably don't want to return to making a weekly manga, especially in WSJ, since it's quite intense to have a series in the magazine, that's why you see a lot of people moving to other places to make manga.
WSJ is still one of the better places where newcomers can get great opportunities to find success and fill the magazine with their fresh ideas and styles. edit: And I want the magazine to stay that way.