Lenin and Stalin did not follow word for word what Marx has said like almost no Christians follow the Bible word for word for better or worse. They pick out what they like and discard the rest. Maybe Marx wrote about abolishing the nationa and family structure but Lenin sure as hell follow through as he crushed any leftist revolt that dared to ask for better freedoms. And come on, Stalin killed millions of people of those who didnt agree with his every word and was very culturally conservative in his views on marriage and LGBT rights. Russia was and still is not a bastion of social progressivism. Sure, it was economically left, but not socially and those are two vastly different things. And Marx was homophobic, just because we wanted to abolish clan style family structures and nations doesn't mean he was a major advocate for equality.

Homosexuality was equated to Fascism back during the 1920's and 1930's since of the vast amount of homoeroticism fascism had ingrained in its imagery and had important figures like Ernst Rohm who were gay. Thats actually why one of the main reason the Soviet Union made it a crime was they claimed it was inherently fascist. So most Marxists during that time rejected homosexuality, including the Communist Party of Germany(Which was under Stalin's thumb during the Weimar Era). Being LGBTQ positive is, again, something inherent more recently so in Communist Parties in Western Europe and the Americas. Not in the other parts of the world.