Yavanna's Chosen

[Raynor]

I see it entirely differently. If we are to judge Radagast on the basis of how well he fulfilled his secondary task of looking out for Yavanna's interests, I would think the Ents would have been the most credible, as they themselves had the fundamental purpose of protecting trees and forests, in line with Yavanna's desire.

Again, ents are very limited in their own focus:

Originally Posted by FotR, Chapter 4

The ents loved the great trees; and the wild woods, and the slopes of the high hills... But the entwives gave their minds to the lesser trees, and to the meads in the sunshine beyond the feet of the forests; and they saw the sloe in the thicket, and the wild apple and the cherry blossoming in spring, and the green herbs in the waterlands in summer, and the seeding grasses in the autumn fields.

We were only a legend to [Men], a secret in the heart of the forest.

The ents' major interest seem to be the really big trees of the forest, while all the rest seem to be outside their concern. That doesn't make them very reliable source tbh. Also, the very fact that they take care of at least the trees in their area, would require very little intervention on Aiwendil's behalf; that, coupled with the fact that ents are rather reclusive and sticking to their own parcel ["we are a legend to [Men], a secret in the heart of the forest"], gives a pretty good reason for their very limited knowledge about his abilities and actions.

We have a single opinion expressed here, by one representative of a race concerned with a limited land, and even there, probably focused on just a few species - everything else, even there (sloe, small trees, green herbs, grasses, etc) seem to escape their notice anyway. If they aren't experts and/or watchers over all these "fields", I don't see why we should be concerned too much with their opinion, if the work of Yavanna has a greater scope anyway.