I would guess that your view of disjointed is entirely disconnected from how it worked last season when the rewards were spread over +2 to +20. With the compression, a +2 this season-4 is like a +12 from last season-3… the rewards are scaled to fit the compression.
I don’t see any need for change. Your arguments seems to be that “raid should be king and only best rewards should be from raid.” Raid on Mythic difficulty does seem to be the pinnacle of multi-player coordination, but there’s no 5-man raid. I know the mythic raiders will disagree, but Blizz has clearly set the bar that +10 (+20 from S3) is on par in mob/mechanics difficulty with Mythic raid.
If anything, I think the added player-coordination required for a 20-man vs a 5-man merits a slight rewards boost for Mythic raid, not a nerf to M+ which the most popular game mode.
M+ was nearly twice as popular as DF Raid per Blizzard’s own poll. Herding 20 cats for 2 hours at a time is a social challenge, not an in-game difficulty challenge, which is likely what M+ is so popular.