And that's fine as long you don't think it is the total picture. But the same traits that make it lighthearted and fun make it slight and forgettable to me.

It was definitely a time of different labor standards but some of what he did was problematic even if you excuse some things based on the era, for example, from Wikipedia:

In 1835, when he was 25, he began his career as a showman with his purchase and exhibition of a blind and almost completely paralyzed slave woman, Joice Heth, whom an acquaintance was trumpeting around Philadelphia as George Washington's former nurse, and to be 161 years old. Though slavery was outlawed in New York at the time, he exploited a loophole that allowed him to lease her for a year for $1,000, borrowing $500 to complete the sale. Heth died in February 1836, at no more than 80 years old. Near the end of her life, Barnum had worked her for 10 to 12 hours a day, and after her death he hosted a live autopsy of her body in a New York Saloon. Their spectators paid 50 cents to see the dead woman cut up, as he “revealed” that she was likely half her purported age.[8][9]