As the article notes, a lot of it was destroyed in an earthquake in the 1960s, so the government seized upon the opportunity to rebuild several major landmarks (like the main post office) in the then-fashionable raw concrete brutalist style.
That said, most of the post-60s residential blocs are not identifiably "brutalist" -- it's not Belgrade -- they're just bland and basically built as functionalist housing in the unloved "Khrushchyovka" style.
But that's not the interesting part. What's interesting is that since ~2010 the government has embarked on a "nation building" (and explicitly anti-Albanian) project with gaudy neoclassical buildings that are often likened to Caesar's Palace in Las Vegas. Kitsch. See, e.g., the fake galleon and its background: https://ibb.co/LTGwYZs
Much ink has been spilled on this matter.
> https://rs.boell.org/en/2021/01/29/neoliberal-manipulation-s...
Thing is, though, it looks good and Skopje is a very fun town to spend time in. The old market is great, the people are nice, and the much-criticized neoclassical buildings give the city a vibe that's both extraordinary (there are very few places like it) and coherent (the entire city is done up in just a small handful of architectural styles.)