Of course it has failed.
I only ever do M+, and my only possible source of upgrades at this point is the weekly vault. M+ aren’t worth doing anymore aside from filling up the vault. M+ quickly transformed from a fun activity into a weekly chore, and this chore is a real time sink.
Do you have any idea how long it takes to do 10 M+ runs? Assuming no leavers wasting keys and an average run time of 35 mins, it takes about 6 hours of M+ to fill up the vault. That doesn’t even take into account the time required to form the group or for people to actually get to the dungeon entrance. Now consider the fact that raiders are expected to invest this amount of time in M+ in addition to their normal raid times (12+ hours combined if raiding 3 hours a day on 2 days per week), and you have a perfect recipe for burnout. I pity those who try to maximize all 3 slots of all 3 rows. The game becomes a job, especially when you throw in daily maw quests and callings.
The worst part is the vault likes to generate duplicates of items I already have. I’ve already had a week where none of the 226 choices were upgrades, and it will only become a more frequent occurrence as more gear slots are filled. If I’m not getting any rewards from any content, then why would I bother with the content?
The grinds and the vault have driven off most of my friends and guildies to other games. They’re all either playing bunny ladies and cat daddies in FF, or they’re killing stuff in PoE.
I hate to admit it, but titanforging was one of the major things keeping M+ alive. Without it, running M+ is worthless aside from the vault. I have no doubt it will eventually be brought back. However, I would suggest a limit to the amount an item can titanforge. +13 ilvl max titanforge (one raid difficulty level) with items being unable to titanforge above mythic raid ilvl level should be enough to address most of the complaints about it from legion and BFA.