As a disclaimer to this post, I understand this is a topic that gets addressed a lot, and not much has changed. Perhaps Blizzard disagrees with its philosophy.
Overall WoW has suffered for a number of years of player burnout or lack of player retention, and I think the cyclic nature of gear acquisition plays a massive part in this.
Right now, a player gears themself up for the current patch and tier, at the start of that tier. The efforts you make for gearing at the end of the tier are not only frivolous but also discouraged. Why care about gearing your character when he is going to be set back so massively in such a short span of time?
The root of this problem is that in it’s current iteration, WoW is not a linear game. You play the patch, not the game. You don’t need to do A to get to B or B to get to C. While some would argue the catch up mechanics and this seasonal way of play makes it attractive for players who may have missed a season because they can just jump into the current action, this argument is a bit misguided. If a player missed a whole season, that means that player missed an entire raid. That entire piece of development time and content is now in the void never to be touched again. This is not good for the developers nor the player. A more linear structure would offer each player more content for a longer period of time.
Imagine a world where people are doing an Abberus run TODAY because they want to hop into Amidrassil before the season ends and they are gearing for it.
Instead if a player is returning today and wants to get into Amidrassil, they do some quests, get higher ilvl than they even would from heroic Abberus, maybe get a crafted piece or two and boom LFR ready.
Is that really good gameplay?
I feel like maintaining a more linear progression in the game would be an overall win for keeping all raids in an expansion relevant, respecting player time and effort while also creating a healthier player retention. No one feels the drive to gear when they know it won’t mater in merely a few months.
TLDR; WoW needs to return to the linear structure of the game, in order to boost player retention and interest. This needs to be done on an expansion by expansion basis.