Click-baity title, but hear me out.
Mythic should have never been made in the first place. Over time like with the devaluating of epics and legendaries, raid difficulty settings have become bloated and lost meaning. So when Heroic was no longer 'Heroic' in comes Mythic to add a new super hard difficulty. Now difficulties have become overbloated and Normal is now LFR 2.0 rather than a fully legitimate difficulty.
The clearest and most intuitive solution to the problem of the difficulty bloat is to simply have Normal and Heroic again. But simply use a scalable difficulty that we've had in the past with raids like Ulduar. I would even go farther and say that Raid Keystones should be a thing, a way to make a Raid tier relevant through the whole expansion even as new content is released. It also means that suddenly the world first race is less important as the relevancy of the first clear of Mythic0 falls away and is replaced with inter guild competition over longer, healthier time frames. it's more important for guilds to go for higher numbers of difficulty and also go back to older raids to go for gear and even tier pieces that are more relevant. This also means the concept of "Tuned for 54 traits" suddenly goes away as well as the base difficulty is rather reasonable and can scale into mathematically impossible, allowing guilds to find their comfort zone for their current gear levels.
Overall this system is healthier than what we have now, which is incredibly polarizing, all or nothing, and at times utterly guild breaking.