Searching "plain shirts" does in fact yield results for shirts without patterns. And "paisley shirts" works too. So it's not such a big deal that negation does

Searching "plain shirts" does in fact yield results for shirts without patterns. And "paisley shirts" works too. So it's not such a big deal that negation doesn't work. Also, "shirts -stripes" does seem to work in both Amazon and Google. Or at least, I see no striped shirts.