The colour wheel they taught you in school is true and almost useless in practice. Complementary, triadic, analogous — fine theory, but it won't tell you whether your palette will survive a real website with a hundred different states.
What we actually do: pick one colour that carries the feeling, then build a working system around it. A warm neutral to sit on, an ink dark enough to read, and one loud accent you ration like it's expensive. Because attention is.
The mistake we see most is too many heroes. Five bold colours fighting for attention is the same as no hierarchy at all. Give one colour the spotlight and let the rest do quiet, structural work.
Then test it where it lives — buttons, disabled states, a chart, a photo it has to sit beside. A palette that only works on a moodboard isn't a palette. It's a mood.