While it is true that plaque can be removed with or without toothpaste, that fact is a little misleading in isolation.

The benefit of toothpaste is the topical application of fluoride. When applied topically in concentrations greater than 1000ppm, fluoride replaces a molecule in hydroxyapatite and creates fluorapatite. Fluorapatite is much more resistant to dissolution by acid. That is important because cavity-causing-bacteria in plaque gain entry into a tooth by bathing the tooth in lactic acid.