I say the opposite, I think that Mythic raid should give zero gear at all and only cosmetics. The best ilvl gear in the game should be obtainable by everyone who puts in at least some effort - heroic raid, +15's etc.. Gear power should be relatively quick to max out on a character if you are playing it properly, say 1 month from the start of a patch your character should be absolutely maxed in any content you choose to do, and everything after that should only be about hunting the achievements, the cosmetics or simply for prestige of having accomplished a victory.
Many people in this game are forced to take part in areas they otherwise dislike just to fully enjoy the area of the game they do like, myself included. For example, having to raid for trinkets and tier etc in order to be competitive in M+. That kind of thing should not exist at all.
Any serious high end gamer will tell you that the gear is irrelevant, they do what they do for the fun of being the best, not because it gives you big number loot. The people who do make that argument are the insecure ones who need that +5 ilvls to feel like they are good.