Just my two cents... I thought Moreland the announcer was much like Moreland the player. Solid, competent, but unspectacular. I thought he did a good job for WGN, just like he did for the Cubs. He brought value to the broadcasts just like he contributed value to the success of the Cubs teams he was on. He knew going in that he had tough shoes to fill in the minds and hearts of Cubs fans, and I think in that regard he pretty much lived up to what was expected of him. In my opinion, he was certainly no "tune out".
As for his departure, we may never know all the details, but I personally take him at his word that the main reason it was time to stay home in Texas where he is roots, family, and connection. He's at the point in his life and career where no one can fault him for that.