Alongside Footlight Parade and 42nd Street these three films really establish Musicals as a genre in film. And a genre for the 1930's era of escapism. This film shows luxury through song and dance. The sets are opulent, the actors are extremely well dressed and made up. The film makes great use of James Cagney as the star of the film running a studio during the depression. And the film tries to portray him as a working man making money in hard times to make him somewhat relatable to audiences. This film provides a spectacle of luxury to the American viewer without directly acknowledging the downside of the industry and the cost involved in creating something so lavish.
This film also deals with the double edged sword of both giving its female characters sexual identity and strength but also reminding the audience that a woman needs to be married.
Hollywood is struggling with this duality of wanting to make sexually desirable women who are strong and attractive with social mores that keep women married and subjugated and weak and reliant on men. This duality is observed by Jimmy Cagney's secretary falling in love with him and doing whatever she can to serve him even if it's clearly not in her interest to do so. The film romanticizes that service of a woman to a man.
On a visual level Berkeley goes off the rails in creating a highly elaborate set pieces and dance sequences that use extras as pieces of a massive symmetrical visual array. This is the sort of choreographing of people to create highly elaborate visuals that we almost only see in events like the Olympics nowadays. It's a massive wonder to organize that many people together and having them synchronize their movements to create complex flowing visually astounding images. And he is a genius for coming up with the idea of shooting these sequences overhead looking straight down at the extras either lying down or dancing around each other.
The most notable sequence and the most parodied is all the swimmers in the pool lifting their legs in unison and making a major visual spectacle out of their aquatic dance number.