Kinda ironic that he starts the article by decrying fancy color palette generators that give you 5 hex codes centered around a primary color, and then ends it by choosing a base color and filling in the gaps with 5 (possibly 10) shades from light to dark. That's exactly what color palette generators do!
The mistake most people do is going hog-wild with color palette generators. The vast majority of the time, you want a monochromatic scheme with a complementary accent color. Adjacent, triad, and tetrad schemes are quite special purpose, and you use them differently. Think of Google - it's a tetrad scheme, but the base color for all Google sites is white, and all 4 colors of the logo are used as accents. You want to KISS - if you do have a multicolor palette, use the colors sparingly and pick a neutral white or grey as the primary background color.
No, not ironic, that's precisely what he doesn't do; he says you probably need 5-9 shades of each colour group - Primary, Secondary, Highlight, Greys, etc.
He also says the reason you can't write a generator is because every colour looks different and needs to be judged by your eyes.
The mistake most people do is going hog-wild with color palette generators. The vast majority of the time, you want a monochromatic scheme with a complementary accent color. Adjacent, triad, and tetrad schemes are quite special purpose, and you use them differently. Think of Google - it's a tetrad scheme, but the base color for all Google sites is white, and all 4 colors of the logo are used as accents. You want to KISS - if you do have a multicolor palette, use the colors sparingly and pick a neutral white or grey as the primary background color.