While I agree that the term is outdated and should just be replaced with "developing", "third world" always had the economic side to it. "First World" countries not only were the major Western powers in the Cold War, they also had the best standards of living. "Second World" countries, despite meaning the Soviet side, also meant countries with a lesser quality of life, where store shelves were constantly empty and people often had to wait hours in line to buy even basic staples like bread and meat. And yet for the most part people weren't starving (except for the Soviet famines in the 1930s or the Chinese one in the late 1950s). This wasn't the case for the "third world" countries not part of either bloc (mostly countries just achieving independence from colonialism) which often had the worst standards of living (largely because their economies, developed under colonialism, never developed a consumer economy as they were primarily geared towards export to the country that colonized them)
Thrid world didn't always have an economic side to it. Third world was coined as a delineation of cold war participation status - it had nothing to do with economics. Switzerland, Austria, Ireland, and Finland were all included in the original definition of third world, but now no longer fit the modern definition of developing nation.
There always was the notion that first-world countries tended to be economically liberal with market economies, whilst second-world ones had controlled economies. High living standards were associated with the first group, for good and bad reasons (and propaganda). And then there are always outliers. Though your example all have moved firmly to the first world since the 1950s.
