I don't think Glenn has grown nor has he regressed. The reason why people think he has regressed is because everyone else in comparison has improved so drastically.
Good point but remember how awesome Glenn was the first time we met him? He was brave and went out on a limb to help Rick out of the tank. He was witty, funny, fast, and confident?! Now he is just sorta there....always a little mopey looking, no real opinions, insecure. I want the baseball cap wearing, fire escape climbing, walkie talkie baring fun Glenn back. I think Maggie and that Glenn would be a perfect duo.