Its the lack of quality control. Kinberg as an overseer should be doing his job and make sure that characters don't over lap Xpecially this is still part of whatever film franchise Wolverin Jackman was part of. Like it's great if the writers have creative freedom. But not this kind of creative freedom where its okay to ignore characters from the previous films.
The X-men franchise doesn't have anything like an "overseer". The film rights were bought by 20Th Century Fox and producer Lauren Shuler Donner back in the 90s. Peter Rice is currently president of 21st Century Fox (exact same title Kevin Feige has at Marvel Studios) and Rice was supervising creative executive on the first X-men movie, launching the franchise. He is likely the one (or one of many other executives) everyone answers to. The x-men films were made much like standalone movies, not as an integrated cinematic universe. Kinberg's job isn't an "overseer", he's a co-writer and co-producer (and now director) on these films.