The Ennui of the Elves

[Lalaith]

I've been mulling over these two quotes from LotR.

The first is from Treebeard:

Elves began it, of course, waking trees up and teaching them to speak and learning their tree-talk. They always wished to talk to everything, the old Elves did.

The second is Gildor, speaking to Frodo:

The Elves have their own labours and their own sorrows, and they are little concerned with the ways of hobbits, or of any other creatures upon earth.

This illustrates how radically the elves have changed over the ages, from being curious, proactive and intellectually inquisitive, to this rather aloof, introspective, even arrogant race.
When did the rot of ennui set in, I wonder? Even in the First age, the Green Elves were I think always more insular than their Noldorin brethren (judging by their differing reaction to the coming of men into Beleriand) and even than the Avari of Eriador and further east - who seem to have been interested in mortals (judging by what Tolkien says about the language similarities between Elvish and the speech of the Edain in the Sil.)
Is the attitude Gildor (a Noldo) conveys just Third Age fin-de-siecle weariness, or did Elvish disengagement with the outside world begin shortly after the Great Journey?