Firstly, just know that the formula "democratic socialist" is itself almost an Americanism (although it's true that Orwell used it). In the rest of the world it sounds suspiciously similar to what the former communist countries of eastern Europe called themselves. And they were most certainly not democracies.

Outside the USA the usual term is "social democracy". That's what the Scandinavian model called itself. Past tense intended.

For examples of successful, free, and equal societies, I would suggest that the best examples are indeed in northern Europe, with a handful of special mentions like NZ or Japan. The HDI is surely the best indicator.

Of countries that have historically used the word "socialist" to describe their political systems, with or without "democratic" thrown in, none are places that you would want to live.

I have family in Sweden, and that doesn't sound like what they talk about. A modest salary - local gov worker or a teacher - seems to be enough for a modest 3bd detached house of a pricing similar to ours.

Where are you getting 100 years? Is that a thing outside Asia?

Clearly no Nordic country is a panacea. But the issues you mention are relevant to a whole bunch of northern European countries, many of which are pretty "socialist" by American standards.

On the oil question, Norway is in any case the international exception. Most countries with oil are not socialist paradises but rather repressive police states. Or semi-failed, like Venezuela. Even before the climate crisis made it unethical, oil was a decent predictor of bad social outcomes. Norway aside, the world's most successful countries, as measured by HDI rather than GDP, tend to have few natural resources. Or almost none at all, like Japan and Germany.

It irritates me that, even today, people keep mentioning oil as some kind of magic solution. It's the opposite and always has been.

Norway being the only exception.