Kees listened to what upstream folk said, but was lead in circles by them, and ultimately his Yama code was vetoed.
I'm not sure what the solution is.
Users can request the protections be added to their distros, which will at least get them better protected, and possibly help make a stronger case for upstream inclusion.
Another possibility is for a company with a strong involvement in Linux to hire someone with the traits a & b above, to act as a system-wide security coordinator / advocate. i.e. make it someone's paid job to work on kernel hardening.