Do you think those words are combinable?
If there is nothing to do, we say there is "no content". Because you simply don't have the option to play the game an achieve something.
If there is something to do, you will do it and eventually you will achieve something. You can say "you beat the content".
The problem is now, if you achieve something too fast, you end up with "there is no content anymore".
If you achieve something too slow, you call it "the timesink is too hard".
So what you actually want is: You do the current content and after you beat it, you want new content ASAP.
So let's say: There is a raidtier which should last 3-4 months. But its nhc and hc version is usally cleared in the first ID. Even the mythic version is getting close to it. You can expect this content to be cleared in few weeks and after that, its a more or less senseless grind, because there is nothing else to beat (except m+, but it's loot is capped so its more or less prestige only).
I know, there are alot of guilds, who take much longer to clear hc and even mythic. You can forget about them, or you can specifically target those guilds, because I think alot of these people are actually those guys who say "timesink is too hard"
One of the best examples is the artefactpower. Is it a steady flow of content or just a stupid timesink? If its a timesink, if you would speed it up massively, you would be capped soon hence there won't be anything to do any more aka no content. I took this example, because alot of people say: you didn't complete mythic raiding, so there is still "content" to do. Artefactpower is basically something everybody wants, and everybody will get by doing varius kind of ingame activities.