What you highlight here is a fundamental difference between what can be accomplished in fiction on paper and what works well for film. The scene you described worked well in the book, obviously, but I can't help but feel you're missing something about the experience, the resonance, of reframing the action of the ents on film as it was done. This strikes me as important because when that scene came up in the movie it was powerful...actually the only real scene in the second film that I distinctly remember, and it was precisely because of how Jackson did it that the event went from "story bit that moves things forward" as it was in the book to "defining point of change" as it was in the film. It was a powerful scene.
There's a lot I disagree with on how The Hobbit was handled, padding being a key issue.....but the LOTR films were outstanding, and at least partially because they were not (thankfully) done as 9 movies instead of 3. This led to a lot of "short cut" approaches to telling the story, which forced Jackson to reach for quicker but more poignant and resonant, emotional events in those films. Unfortunately, had they been made now in the same manner as The Hobbit, we not only would have gotten that lengthy debate among the ents you suggest, but it would have been 30 minutes long and involved lots of slow motion and drawn out voice-modulated speeches.