The fact that minority communities split off to form societies with left policies in no way supports the idea that they treated minorities within their own group better. Giving more economic power to the majority (even in a true democratic socialist system) simply means that they hold more power over the minorities. It is absolutely what has happened in every example that’s scaled and I can point to multiple genocides to support it.
It is why most intellectual left academics focus on anarchism which has it’s own issues in terms of rights protections, productivity, and central coordination in a system without a market.
Just like fascism needs a unified society including corporatocracy to succeed, so too does left ideals need resource control. The flaw is baked into the system at it’s core and nothing eliminates people’s natural tendencies to be exclusionary. Every society deals with it. Fascism deals with it by eliminating it. Left societies deal with it through resource control. Liberal societies enable base protections of property that show clear indications and recourse when rights are violated.
There are clearer takeaways and examples if we focus on one ideology within these groupings ie Nazism vs Francoism, classic Leninism vs modern anarchist thought, or classical liberalism vs neoliberalism.
Ultimately, if a country like the United States of America were to magically change to a classic communism model overnight with no bloodshed, you didn’t make it less racist. You just handed the majority more power over the minority. If your worldview includes that education would make the difference, it could and should under any model. 90% of the time when true left leaning folks say they want change in the system, it’s because they want to force through their ideals, not that there’s anything built into their proposed system to actually keep it that way.
This is largely why the American left shifted to a reform mindset in the '60s. Not only were they not getting the results they wanted with their approach, they were watching the atrocities happening in the East combined with the civil rights movement and decided that maybe they shouldn’t be fighting to give more power to the majority without some kind of economic check on power. It’s why you started seeing institutional changes combined with legal protections, education, and social shifts instead of radical changes. There is no radical change that can fix things, it takes a wholistic approach.