For many vegans, health isn't the big issue. I've used this system to come up with a sort of 5 Food Group System. I have modified it a bit. The fun thing about this 5 Food Group System is the food groups are called Wood, Fire, Earth, Metal, and Water. So, if you eat these things, because you're missing the other phases, you will crave these.
More balanced meals help.
They should just enjoy themselves if they don't like it. There is no obligation to eat healthy food, it's a choice. It doesn't matter, but there are consequences to everything we do. So, eat what you want, and don't complain. Now, if you don't like the taste, something may not be cooked right.