"With the moving 'Good Bye Lenin!' we get the message loud and clear that not all changes to East Germany were for the better, no matter how good the intentions."
That's the message you took from the film? You must have already been a socialist or had socialist leanings before watching because your interpretation sounds really biased to me. What I took from it and what his narrative at the end communicated was that his mother was someone who truly believed in the utopian propaganda of socialism. That she lived in denial of the reality of what it had done to them. Look at how it split up their family. His father didn't flee to the West because where he was at was a nice place. The tragedy of it was that she had given so much of herself and her life to this ideology that basically was a fraud.