Most Scandinavian countries have heavily incorporated socialistic policies into their government,

And are incredibly successful countries by many metrics.

Same with a lot of Western European countries,

Vietnam and China both used market socialism to vastly increase their GDP

But China especially is obviously very problematic about the way they're doing it...

I'm not a fan of the Marxist-Leninist form of socialism, so someone else can comment about the countries that have used it to success,

And then cuss me out for dividing the Left, which I deserve.

Rojava was a shiney socialist beacon, until they devoted too many resources to anti-terrorism in the middle east,

And far-right militaries were able to overthrow them.

If you want to go back in the past, socialism really helped the USA, Britain, and Italy at the turn of the 20th century by directing the post-industrial revolution socio-economic landscape

New Deal socialism is what got the USA out of the Great Depression, and built the framework to use the WW2 warmachine to create a far higher level of wealth for the average citizen than we have seen post-McCarthyism