What the title suggests.
I personally hate Catch-up mechanic, they invalidate the hard work people put in the earlier stage of the expansion, yet, I understand they are a "necessary evil" (So to speak) for the good health of the game because it feels intimidating to go through multiple tiers just to gear up and be able to reach the final tier. Having a catch-up mechanic encourages people to come back and not feel they are terribly behind.
Yet, with the state of Mythic+ Seasons, it becomes necessary to scale loots every 6months with the release of new raid. In 1 month time with the release of Battle for Dazar'alor raid, base Mythic Dungeon will reward 370 gear, and Mythic+2 Cache will reward 380 gear, which we can only get right now doing Mythic+10.
As a result, I don't see the point of progress my character at all. For all the hardwork, I get to enjoy the power for about 4months (I am not hardcore enough to kill M10 or Mythic raid in the first month or so), before the next M+ season kicks in and every newly lvled 120 has equal or even better gear doing 10% of the work.
I miss the days where I get to enjoy the power for 2 whole years, 1 year is fine too, but now 6months (Or less) just doesn't feel worth the effort.