To voice an opinion as someone who has been hanging around here there are some topics that show up that to be honest that any kind of feed back, at this point, from Epic would only add to the confusion with out first establishing the problems that needs to first be resolved but traditionally “is” resolved in due course with the ever evolving updates to the engine.
The problem in regards to the use of Root Motion over network is not an issue that it can not be used to coding and replication requirements but by the very nature and differences between in-place and Root Motion as created asset sets as part of the over all game design.
Bottom line animators, content creators, love Root Motion as all asset of the movement of the player model is contained with in the root motion data and is triggered via an event as to the desired action which includes speed, direction and location relative to the root of the player model as “authored”
In it’s current implementation as being event driven there is no way to track the XYZ location of a given player across the network in the same manner as you could create the identical physics event for say an explosion where the result as to an event has to be “identical” from one client to another.
Talking to our coders they hate root motion as to the demands of the network code to be able to update client information as to be the correct response as to an event driven being driven by the movement component that already contains the necessary requirements as to error correction.
Root Motion does not require the use of the movement component and is why you tell Unreal 4 “not” to use the movement component by telling UE4 that it is Root Motion based.
The bottom line as to network needs it would be like trying to fit a square peg into a round hole and until there is a component that manages the client to client requirements that ensures a sync to the “event” driven data the requirement of all clients knowing where the player is in relationship to world space is a very difficult task as to net-code being voodoo magic by nature.
As a perspective net-code is a place where angles free to trend.
My assumption based on the lack of Epic feedback is they by now obliviously know the the use of RM over network is a known issue and as in the past will speak up “once” there is a working solution and will in due course come up with yet another impressive solution.
P.S. As an animator being able to author using root motion makes life easier and adding the ignore RM flag is/was a feature that at least wanted so if and when RM over network becomes possible our project is future proofed as to desire.