So there's quite a few threads about people raging over their key being wasted, etc etc.
I get it, you wanted a run and it fell apart and now you're mad online.
It happens.
Lots of people have thrown out ideas like "give them deserter for burning the key" and the like, but really, the problem isn't so much the people leaving as it is the fact that keys, as a concept, are just, well, kinda dumb.
The best way to implement this system, to appease as many as possible (IMO, ofc), would be to do it like grifts in diablo.
I know, I know, I said the no-no word, but in all honesty, it would be the best system.
The concept is sound; you unlock higher M+ levels by doing the lower ones.
Every season, everyone starts at +2, can do any dungeon available in rotation, then by clearing it, +3 unlocks (or higher, if you 2key it and such).
You don't need a key to start the run, you just simply get a menu on the podium that says "choose your difficulty".
The difficulty unlocks are dungeon-agnostic; clear a +10 in RLP, open +11 for all 8 dungeons.
In terms of what difficulties are available on the podium depends on the group, as it will show the highest common unlock.
If 4 players have +18 unlocked but one of them only have +16, then +16 is the highest open to that group because it's the highest common difficulty available for all party members.
Gone are the days where you need RNG key to do the place you want to target, nor do you need to look through LFG to find someone with that key.
You can simply make a group for the dungeon of your choice and the difficulty of your choice, up to the max level you have unlocked.
If you post a +15 Temple, then someone who has only opened +13 on their toon at their highest just can't apply, so you now you are only getting people who have cleared at least one +14.
The M+ rating can still stay; you still want to time each dungeon at the highest level you can, and everything else around M+ can remain the same, this just removes the requirement of a key in someone's bags.
If you clear a difficulty level, you are the key. That toon can do it for the rest of the season, no worries.
It only applies to the toon you are playing, so you can't just ding fresh 70 and get carried through high keys; you have to work your way up.
This may be a downside to some who play shitloads of alts and such, but the good news is, you only have to open difficulties once per toon per season and you can choose the dungeon you do it in, so if it really bothers you, have people carry you through the quickest one, clear the timer with ease, rank up your difficulty to your target in an afternoon of play.
Sure, there would be kinks to iron out, but overall, it gives everyone access to any dungeon they choose at the difficulty that suits them.
It also prevents the whole key burning stuff that results in downgraded keys and frustration.
If a run goes tits up, and it will happen from time to time, people lose their time, they get angry, then they also have to rebuild their key.
Let's remove the "rebuild your key" aspect to relieve one layer of stress.