Well in theory Root Motion is nothing more than just another form of input that just like a joystick, keyboard or mouse, and could be used to reshape the output even over network but at the same time retain the original fidelity of the original. The best of both worlds as all things involving animation is based on RM… except video games.
Understandable there are issues relating to network play but is not the root of the problem, pun intended, but rather the lack of proof of concept that it’s use in both single as well as network play is a better solution over and above what has been tested over years worth of games development.
It comes down to.
Animators and content artists love RM because it maintains fidelity
Coders hate RM because it means more work to make it work as well assume that some how it takes their ability to control game speed and physics away (their version of mocap 
)
What it will take to get past the wall so to speak is proof of concept, as well as a RM movement component, demonstrating a full out network compatible mini game so that how it can work could be proven with out having to put in the necessary R&D over and above what has already been proven to work.
After that I could do pages of why I prefer RM over in place but the best is the player will always be grounded, which seems to be a word use that I always have to explain