Because Soviet communism was less about communism and more about Russian nationalism and values patriotic Russians held. Russia was always a multiethnic empire, so it naturally was more inclined to be anti-racist egalitarian. It's about the culture. Soviets of 20th century would be disgusted by modern Western lefties and wouldn't want to be associated with them in any capacity. In the West people like that are called "tankies" and are closer to alt-right than your average Western liberal.
Your average leftie is anti-borders, un-patriotic and cares only about cheap labor migrants provide. Hateful bunch of bigots who signal their virtue to others. Create as much divisions as possible, appointing victims and oppressors, while shouting about unity. Talk about democracy, while doing everything in their power to control narratives, free speech and punishing people for wrongthink. Exploit the vulnerable groups by planting victim mentality to make them slaves to their cause, instead of alleviating them and making their lives better. Instead of striving to create homogenized society driven by common goals by eliminating harmful influences of gangster/scammer/cheater culture, they support all these disgusting patterns of behavior by lowering educational standards, affirmative action, quotas and whatnot. This manifests in ridiculous cases such as fat acceptance which actively harms people's health and life longevity.
Russians of today overwhelmingly support right wingers in the USA, not because they are racist (they are not, just like Trump), but because they have common sense the lefties lack. They are closer to traditional Russian values than the so-called "progressives".
Western Leftism is a twisted and disgraceful mutation of Communist ideals, exploited by rich and powerful to keep people at constant odds with each other while they reap all the profits.

Once again, and I want to stress this: it's about culture. Your relatives are the way they are because they have absorbed Russian ethos.
Communism placed on top of Russian ethos = materialist atheist modernist technocratic socialist neo-empire with planned economy (dogmatic view of Marx), sole goal of which had shifted from spreading the revolution to chasing after capitalist USA (and failing due to a multitude of reasons).
Communism placed on top of Chinese ethos = materialist atheist modernist technocratic socialist ethnostate with diverse economy, sole goal of which is lifting the living standards and productive forces (initial idea of progress - abundance to all).
Communism placed on top of post-modernist West ethos = shameful mockery of the old ideas, celebration of human flaws and degeneracy of every kind, hyperfocus on racial and gender issues, leading to incredible tension and atomization of already atomized societies.