In effect, each character now needs to “unlock” 140 of the ilevels on their gear set. You get 6 ilevels worth of points for each Mythic dungeon you do, but you can only use them in chunks of 5.
I think other types of gameplay probably give you points too but I don’t know what they are. Is the Raid Finder still a thing? I mean the thing everyone used to call “LFR” with such regularity that even Blizzard PR kept forgetting it was called anything else.
ilevel unlocking is also an effective nerf to offspec roles, (depending on your level of dedication) which pisses me off only slightly less than the first reason.