No-one eats just one source of plant protein - in a balanced vegan diet you are eating lots of different foods so get all your essential amino acids that way. For example, while wheat isn't a complete protein source (who eats just wheat on it's own, anyway?) combining it with chick peas - as in hummus and bread/pitta - makes it complete. There are also some plant proteins (like hemp, quinoa and buckwheat for example) which are complete.

You're correct in saying, of course, that we need to make sure we get enough of the various vitamins and minerals essential to good health - this goes for everyone, not just vegans.

Similarly, avoiding 'toxins and antinutrients' is an issue for all of us, not just vegans. You only need to look at all the pus cells in milk (The average somatic cell count in U.S. milk per spoonful is 1,120,000) or the carcinogens in various meats to see this is not a vegan issue.