Regarding historical context, it goes without saying that the scenario ignores every 19th century reality except, to some degree, sets, costumes and of course the social and racial prejudices of the time, but only to score identity politics points. Of course, with writers like Jenny Bicks (very much at home in the 1990's world of "Sex and the City") and Bill Condon (whose uneven depiction of James Whale in "Gods and Monsters" was made bearable by Ian MacKellan's inspired acting and whose "Kinsey" was a bore) you're not going to get much of a feel for past eras.
The score by the "La La Land" team of Justin Paul and Benj Pasek is almost entirely forgettable. The previous film had one catchy tune ("City of Stars"). The music here is boilerplate, the lyrics only very occasionally above banal (if you can hear them; most of the songs begin clearly and softly and intimately but quickly expand into heavily orchestrated extravaganzas which mask the paltry musical and lyrical substance).
As for casting, you can hardly miss with the charismatic and multi-talented Hugh Jackman. Michelle Williams as his wife is largely wasted and gets stuck with some of the most embarrassingly obvious dialogue. Zac Ephron, who seems to be thickening in his middle age, plays an invented character, a high-society playwright who is miserable and empty until he teams up with Barnum, exchanges the pen for the emcee's baton and falls in love with an African-American trapeze artist (Zendaya).
The film is reminiscent of some of the low-budget, episodic but energetic biopics that rolled off the Hollywood assembly line in the 1930s except here the spending is lavish and the song-and-dance sequences, which at their best advance the narrative rather than overstate the obvious, are eye-poppingly elaborate. There seems to be a deliberate attempt to recapture the sentimentalism and syrupiness that was commonplace in many old-time movies, but mixed with the 21st century mindset of the writers and director, it becomes self-parody.
The main message seems to be the old reliable one: love is the most important thing of all, even more important than material success and it's better to put love first, and that we all, no matter what we look like or where we come from, are valuable individuals worthy of respect.