The “rags-to-riches” trope is one that is used throughout many different movie and television genres, where the main character living in a bad situation is able to push through to end up in a position with more wealth, power, or fame.
The message we take from this is that while hard work is admirable, it can quickly become exhausting if there is no time built in to play.
In the story of Tarzan, learning that he belongs to an entirely different species than the one he grew up with is challenging for him, his gorilla family, and the other humans he meets.
The main premise of the movie is that even though all the animals have become “civilized,” there are still prejudices against the different species.