That's the original definition. I think now first, second, third are used to annotate which level of development a country is at. Especially that now, not all developing countries are equal.
It's more nuanced than that. First was the USA, the first nuclear state (and the west / allies). Then the Soviets. The Third World was the anticipated rise of the nations that would join us on the world stage, a hopeful and optimistic term[0]. Then we deliberately sabotaged them and kept them under our boot to extract resources.
Third World is now a slight for developing nations.
The commenter doesn't recognize that nordic countries have exceptionally high quality of life despite less sunlight (a common cause of depression) than whatever country in which they likely reside. They aren't curious about the world enough to learn about others.
First world is a political term meaning non-aligned with the West or Communist states during the Cold War.
Historically, Sweden was a non-aligned country. The very definition of a “third-world” country.