I was impressed by a little-known Slovak film called “Inferno” from 2014. It is a very dark movie about the grim post-socialist reality in Eastern Europe. It depicts all the problems - oligarchs, suppression, intimidation and subversion of leftists, collapse of social norms and social programs, extreme poverty etc.

https://www.imdb.com/title/tt3219106/

One more movie is Peepli [Live] from 2010 - an Indian movie depicting extreme poverty and suffering in rural India, as well as the indifference of more wealthy Indians to it.

https://www.imdb.com/title/tt1447508/

They Shoot Horses, Don’t They? (1969) by Sidney Pollack. Desperate people participate in a cruel elimination show for the wealthy during the Great Depression. Maybe this film began the well-known now “death games” sub-genre, not sure. It was probably a new topic when the film came about.

https://www.imdb.com/title/tt0065088/

You probably know the recent “Parasite” (2019) movie. Not necessarily leftist, but it still depicts South Korean social tensions well

https://www.imdb.com/title/tt6751668/

Maybe it is off-topic, but I could also suggest a South Korean TV series “Good Manager” - drama/comedy. It depicts South Korean corporate corruption quite well and other problems of chaebol system. It has a social justice spirit, but it is not very strong. After all, being an open socialist in South Korea is dangerous, as I understand. Watching it was both fun and informative, however this is not concentrated materiel of course

https://www.imdb.com/title/tt6352982/

It is noticeable that in the capitalist world there are many anti-capitalist movies and they become more and more popular, but practically none pro-leninist movies (depicting the role of organizing, party as the vanguard of the revolution, dictatorship of the proletariat etc.) or movies depicting the people’s control over economy/real people’s democracy… when it comes to showing socioeconomic problems American movies become extremely primitive and absolutely never offer solutions (except the pro-systemic “the bad guy goes to jail” ending)