One of those "too much of a good thing" type of situations.
Casual/semi-hardcore guilds always have something to do. Hardcore/WF guilds have too much to do.
Right now, you can clear mythics before the next patch comes while raiding 2 hours a day, 5 days a week (or 3 hours, 4 days).
Or you can just go Mythic+ bananza and get almost the same gear.
I've maintained two almost equaly geared chars (both 890 at the time) on the same AP level without any problems. HPally was on raid progress, RDruid didn't even step a foot in a raid. Go figure.
But you can't do both on 4+ charachters and not feel tired after a while. Multiple gear sources and gear variations tied to a random number generator are OKish, if you do them one at a time or in moderate amounts. Not all of them all the time. That's where the burnout for WF guilds comes in.
Still, it's funny (or sad) that guilds "go casual" after three weeks of progress, when Rag in MC was killed almost 5 months after it's release.