I guess I just don't see it as optimistically as you do. Don't get me wrong, I definitely understand how the idea that anyone, even the poorest and simplest of shephard boys, could exalt as a Terrestrial would be incredibly uplifting and hope inspiring to the population of Creation. But what kills it for me is the fact that it's really no different from the lottery. Yes, anyone can win the lottery, but realistically you shouldn't expect to because the percentage of people who do win the lottery is statistically so small that there is an almost zero percent chance of you exalting as a Terrestrial (roughly .005% to be exact).
Now just to be clear, I'm not trying to make Exalted more bleak or grimdark or anything like that. I simply prefer it when a mortal says "fuck this, I don't NEED an exaltation to be a hero" and goes off and saves people to the best of his ability in spite of the fact that he has no exaltation. That's the kind of story that I love more than anything, and I think that Terrestrials aren't really made for that kind of story.