PoP is really the pinnacle of the ideal they started towards when they first made the game, I agree. The only compromise imo was Plane of Knowl she having portal stones. Taking out the druid / wizard travel economy made the world a lot smaller. But otherwise, as far as the idea of questing forever, PoP era has just the right amount of content and alternate progression. And the encounters were just the right amount of challenge without being beat-your-head-against-the-wall-til-the-next-expansion's-level-cap-increase hard.
And then LDoN also was a little too much "forever" for the amount of reward you got from your questing y'know?