Everything Anet does, will diminish over time, thats just normal for every game.
Nothing will entertain you forever, without that you have to do something, or that you will find yourself repeating something, that you have done already alot of times.
Scavenger Hunts are no grind, they can become grind, if they aren’t well designed, but just by themself they are no grind. Its their design that can make them that, if you have to do certain tasks like tons of times, due to some items that you need having like only a 0,01% drop chance, or due to stupid mechanisms slowing you forcefully down, like time gated crafting >.>
That are bad designs, that must not be and which belong changed/removed!
Scavenger Hunts, when well designed can be so much more fun and grindless.
At least you have to admit, this kind of grind, if it gets not well designed implemented is still alot better, than having to rely yourself 100% out of all cases on just 100% pure luck to get a precursor dropped from the MF or as a loot drop.
It would be a definitive quality of life improvement to have finally features like Precursor Crafting and Scavenger Hunts – which are for me features, which should have been in the game from begin on … because with those features in the game from begin on, legendaries would never have become such a massive grind, like they are now due to Precursors being way too much luck based to get currently.
But then on the other hand, grind is defined by every person diffferently.
What you define as grind, must not be grind for me. Its subjective for everyone.
Personally I like the idea behind sub classes ~ quoted from Chris Whiteside