Originally Posted by
Slicer299
All I see in these changes is Mythic+ being limited to provide the rewards it is designed to reward in the first place. Mythic+ is not, and was never, intended to be a method of farming Artifact Power. It's a form of content intended to provide you with gear upgrades, that's it. As such you should only ever be running Mythic+ dungeons keystones at levels high enough to provide you with gear upgrades.
Now, part of that process does include leveling up your keystone to those higher levels. But that's why your weekly chest gives you a keystone that is already partially leveled for you, to cut down on the amount of time you need to spend upgrading it. And the new system keeps in place the existing keystone upgrade system of upgrading the keys by +2 or +3 levels if you complete the keystone with a significant amount of time remaining.
Once you are geared up and Mythic+ is no longer a reliable source of gear upgrades, it's intended for you to stop doing the content. Unless you feel the chance at a Titanforge upgrade or the increased legendary chance in your weekly chest is worth the time. But the AP reward from the content is strictly a reward from the time you put in, not the goal of the content itself or an incentive to do the content. If you don't need/want the gear, and/or you don't feel the gear is rewarding enough, don't do it.
There is also the challenge aspect of Mythic+. It's why the item level of the gear stops increasing, even though you the level of the keystone can go higher than the point the item level stops increasing. Because some people like do run the highest difficulties in the shortest amount of times strictly for the challenge of it and the bragging rights on the leader boards.