Doing some more thinking about this, and the aspect of story and whether or not they are declining or not over the years. Break it down this way. In the early years of Disney animation you had films such as...
Snow White
Achieved her happily ever after because a prince fell in love with her beauty.
Pinocchio and Dumbo
Achieved their happily ever afters because a little sidekick saved them from literally every scrape they found themselves in.
Cinderella
Achieved her happily ever after because a prince fell in love with her beauty.
Sleeping Beauty
Achieved her happily ever after because a prince fell in love with her beauty.
The trend I am seeing in lessons taught in the earlier films... You are born with beauty or lucky to have a smart sidekick.
Moving forward to the Disney Renaissance, which is a favorite era of cinema for many.
Mermaid, Beauty and the Beast, Aladdin, Lion King.
All achieve their happily ever afters because they are either born into royalty, or marry into royalty.