The problem with dropping recipes is that you only need to get it once, so that doesn’t work for that sort of model of “endgame” that Aridhol was talking about, even if it’s a super low (below 0.1%) drop rate, unless it’s the sort of recipe that you can only use X times and then you need to get it to drop again.
Guilds would just farm it until it drops and never have a reason to kill the thing again, and the problem he was talking about is people feeling like there’s nothing left to do in game because they already have everything.
That sort of “Endgame” Is not my cup of tea but lots of people think they need such a thing.
The only way I can see to fix that in a more permanent way without requiring new stuff being added every month is if the items dropped are consumable in some fashion, or otherwise time-limited. Costumes that only last X days, for example, or recipes that you can only use X times.
I still think that temporary power-ups in the form of augments that make old items behave in new ways would be the most interesting. Kind of like getting an artifact / unique item in games like Path of Exile / Diablo, that can drastically change how you play the game, except it only lasts for a little while.
Basically, something that can trick people into feeling like they haven’t got every item in the game.