I wonder if they are discouraged by the experience of Con Kolivas[1] who proposed an alternative scheduler back in 2007. (Apparently he is still maintaining his "-ck" fork of the linux kernel[2]!)
I only mention this as a historical case that has remained in my memory. Maybe Linus is willing to revisit the issue, I don't follow LKML.
[1] https://en.wikipedia.org/wiki/Con_Kolivas
[2] http://ck-hack.blogspot.com/2015/12/bfs-467-linux-43-ck3.htm...