That is literally how Raiding works. To be more precise: WORKED in the past. Untill alternative means of gearing were introduced.
And those alternative means what they created is that atleast half the raid in any difficulty was cleared in 1 week and then nobody wanted to do it again. Why bother?
In the past (as I said already) there was a purpose to “farming runs”. To gear up people such as to progress in progression bosses. That process, by design, was made to take X amount of time. Which was the life-cycle of the raid in question.
Today “farming runs” dont exist anymore. And blizzard is trying to balance out gear aquisition as best they can. Its what you observe today.
Also, this:
Is what RTWF and Title guilds do. Because they can.
The rest, we have to “nerf the boss” by gearing up slowly because we cant play 24/7, or got the skill to raid practically naked. The question is: How long do you take to get there?
My guild takes ~ 1 to 2 months to reach this state with the Heroic Raid. Once its cleared, then people stop playing untill next patch. And many are not even fully geared yet. All they have is their CE achevement, killed the last boss and DONE.
The difference with mogs is that mogs can only appeal to a fraction of the base. Not everyone likes a “red armour”. But a 20 ilvl increase (bigger yellow numbers) is something that appeals to broader audience.
That is why they are not equivalent.
And what do you propose? To add mythic tarck +++ ? Or to drop the ilvl rewards of delves? We are back to square 1 then. Back here discussing the same thing but with a different ilvl number.
If gear is the problem, but changing rewards solves nothing. Maybe gear is not the issue to begin with. Maybe its something else.