Any society where Marxist doctrines came to predominate ended up suffering for it. We can quibble over what you call the USSR, but Marxism is simply a-economical, and causes unimaginable human suffering to the extent that laws are shaped by it.
>>Marxist "doctrines" also led to 5 day 8 hour working weeks, paid leave, unions led to increased wages, and many other workers rights. Hell, before the left wing gained power, child labour was predominant in capitalist economies.
No it didn't. All of those things emerged as a result of the rising levels of per capita GDP that were due to profit-motivated investment in a free market.
Child labor could only be abandoned when productivity increases enabled parents to support their whole family alone, and that productivity increase was, again, a consequence of profit-motivated investment in a free market.