I started in agreement, then I realised
given watching the irreverence much of the player base has for anything that doesn't accelerate their savage progress, you would have lots of people just picking up the first quest and then disappearing, hollowing out the community aspect.
Then you'd have people picking up the first quest abandoning it, so it doesn't go into their log and complaining to support.
Then if they did allow evens to be finished whenever they'd have to be more careful about designing every event to be soloable, and complaints of they don't. (Many have involved Fates of one sort or another)
I get OP, but it actually seems quite unworkable really.
No therr has to be some incentive for lots of peole to be in certain places all at the same time.
In fact I think game+ style only be available during the event in question.
However, seperate matter, but events should never be recycled, but rather every event should be new +2 or more old ones.
(There is no need to assing blame and say people are 'at fault' for not finishing content though.)