No, I don't believe there is anything more to it. I explained why I believe assisted suicide was a needed plot element. I do not believe that just because something I disagree with is in a movie, it is propaganda. You might have a point if the movie centered on the issue, but it doesn't. Or if the director was a repeat offender, but Clint does little besides expertly direct movies. What is the message of his other films? You would have better luck convincing me that The Aviator was pro-mental illness because it showed Howard Hughes acheiving with several.
What planet are you from? The only thing the average person can think about on the way out of that movie is the manner of her death. To say the movie didn't center on it is to say that only because it occurred at the end. In many ways it was like Miller's "The Crucible" Starts out slow and builds to an unexpected climax of death. An ending you can't forget.