Anet doesn't allow grinding
If this is actually the case, it’s a beautiful thing. It prevents grinders and farmers from locking-down event chains, keeping them from evolving naturally. That way the events can cycle naturally and wont get stuck into a 1/2 eternal cycle while others are not triggered at all.
There are Diminishing Returns that you may have triggered. It should only happen if you do the same thing over and over though, not if you do a variety of events.
It’s not done to prevent grinding, it’s done to make grinding less profitable than regular gaming. If you enjoy grinding, you can still grind without the rewards. If you only do that because of the rewards, sorry no cookies for you. Go play the game instead.
Yes, the game incentivises varied and engaging gameplay over easy, repetitive, boring farming. If “how you want to play the game” is to get rewards with minimal effort and engagement, then yes, you should be denied it.
(No CoF nitpicking, please, I’m well aware.)
The features there to keep people from getting too well rewarded for doing the minimum amount of work. It’s to incentivize exploration and participating in new activities. Granted that diminishing returns can be a harsh mistress sometimes but all it takes is a few minutes spent on something else and then you can come back to what you where doing. Look at it as less of a punishment and more of a breath of fresh air.