The relevance of M+ is directly tied to raids. You only care for the higher ilv gear because it is merely a necessity to progress in raids. If you're not raiding, you shouldn't be worrying about ilv pursuits to begin with.
Fact is, M+ is impossible to balance. You have a group make up of 5 people instead of 20, so by design you'll have a group excluding any class that can't bring hero, brez, and stuns/CC.
There is virtually zero reason to bring a priest or feral druid, for example. That won't change short of giving them utility competitive in power to spells of such magnitude like hero/brez/stuns.
Then there's the fact that the variety of keys and the design of aoe will necessitate that all classes be capable of aoe burst and CC, since that's what favor M+ for the time being.
If you balance all classes to have aoe burst and CC, you introduce problems into raids where they'll just pick the class with the highest ST/boss DPS since aoe is no longer a niche to justify bringing in low boss DPS specs like ele shaman/balance druid/ret paladin.
You'd also wildly overpower the dot specs since by giving them strong aoe they'll also dominate council fights, leaving only patchwerk bosses as a possible weakness, of which there are very few.
I agree that ramp up and immobility are shit weaknesses to have without being turned into arcane mages on steroids to compensate for the lack of mobility and burst. So I'd rather they reduce the degree of such weakness rather than eliminate it outright, while providing talents to fill in a niche when necessary.
An example of this is affliction's doombolt. With this new talent, affliction will have competitive contribution to priority adds, at the cost of sustained DPS and cleave (if haunt turns out to be better ST sustained DPS).
I think the best way to make M+ more accessible is to deemphasize trash mobs severely.
To me, for M+ having been a tank main, there has never been an encounter where I think trash is less dangerous than a boss. The trash are the tank's main headache and where I'm using most of my cd's, which makes no sense.
Keep trash, well, trash, and balance the dungeon along extra mechanics for boss fights.