Bcachefs was not kicked out because its design and implementation is of bad quality. A bad quality software is something that is: full of bugs; every 4 fixed bugs you introduce a new one; the design is so wrong that it is difficult to add new features; the code is difficult to understand.

If you consider various metrics like irrecoverable loss of data, lines of code, features, Bcachefs is a very good project. It is under development, so the source code is not "stable" and there are frequent updates, but the behavior of the file system is fully under control and it is only improving,