THe biggest most insurmountable obstacle in mythic raiding is getting 20 people together who can all simultaneously come together and have free schedules 2-3 hours a day multiple days a week and actually have to be legitimately good players who know what they’re doing.
I have no idea what they need to do to make that work, but my alternate answer is bring back 10 man raids with appropriate mythic track rewards. Atleast that is my #1 preference (which I understand isn’t happening).